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1 | \input texinfo |
2 | @setfilename stabs.info | |
3 | ||
4 | @ifinfo | |
5 | @format | |
6 | START-INFO-DIR-ENTRY | |
139741da | 7 | * Stabs: (stabs). The "stabs" debugging information format. |
e505224d PB |
8 | END-INFO-DIR-ENTRY |
9 | @end format | |
10 | @end ifinfo | |
11 | ||
12 | @ifinfo | |
8c59ee11 | 13 | This document describes the stabs debugging symbol tables. |
e505224d | 14 | |
612dbd4c | 15 | Copyright 1992 Free Software Foundation, Inc. |
e505224d PB |
16 | Contributed by Cygnus Support. Written by Julia Menapace. |
17 | ||
18 | Permission is granted to make and distribute verbatim copies of | |
19 | this manual provided the copyright notice and this permission notice | |
20 | are preserved on all copies. | |
21 | ||
22 | @ignore | |
23 | Permission is granted to process this file through Tex and print the | |
24 | results, provided the printed document carries copying permission | |
25 | notice identical to this one except for the removal of this paragraph | |
26 | (this paragraph not being relevant to the printed manual). | |
27 | ||
28 | @end ignore | |
29 | Permission is granted to copy or distribute modified versions of this | |
30 | manual under the terms of the GPL (for which purpose this text may be | |
31 | regarded as a program in the language TeX). | |
32 | @end ifinfo | |
33 | ||
139741da | 34 | @setchapternewpage odd |
e505224d PB |
35 | @settitle STABS |
36 | @titlepage | |
139741da | 37 | @title The ``stabs'' debug format |
e505224d PB |
38 | @author Julia Menapace |
39 | @author Cygnus Support | |
40 | @page | |
41 | @tex | |
42 | \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ | |
43 | \xdef\manvers{\$Revision$} % For use in headers, footers too | |
44 | {\parskip=0pt | |
45 | \hfill Cygnus Support\par | |
46 | \hfill \manvers\par | |
47 | \hfill \TeX{}info \texinfoversion\par | |
48 | } | |
49 | @end tex | |
50 | ||
51 | @vskip 0pt plus 1filll | |
899bafeb RP |
52 | Copyright @copyright{} 1992 Free Software Foundation, Inc. |
53 | Contributed by Cygnus Support. | |
e505224d PB |
54 | |
55 | Permission is granted to make and distribute verbatim copies of | |
56 | this manual provided the copyright notice and this permission notice | |
57 | are preserved on all copies. | |
58 | ||
59 | @end titlepage | |
60 | ||
899bafeb RP |
61 | @ifinfo |
62 | @node Top | |
63 | @top The "stabs" representation of debugging information | |
e505224d | 64 | |
612dbd4c | 65 | This document describes the GNU stabs debugging format in a.out files. |
e505224d PB |
66 | |
67 | @menu | |
139741da RP |
68 | * Overview:: Overview of stabs |
69 | * Program structure:: Encoding of the structure of the program | |
6897f9ec | 70 | * Constants:: Constants |
139741da | 71 | * Example:: A comprehensive example in C |
e505224d | 72 | * Variables:: |
8c59ee11 | 73 | * Types:: Type definitions |
139741da | 74 | * Symbol tables:: Symbol information in symbol tables |
8c59ee11 | 75 | * Cplusplus:: |
e505224d PB |
76 | |
77 | Appendixes: | |
139741da RP |
78 | * Example2.c:: Source code for extended example |
79 | * Example2.s:: Assembly code for extended example | |
8c59ee11 JK |
80 | * Stab types:: Table A: Symbol types from stabs |
81 | * Assembler types:: Table B: Symbol types from assembler and linker | |
82 | * Symbol Descriptors:: Table C | |
83 | * Type Descriptors:: Table D | |
139741da RP |
84 | * Expanded reference:: Reference information by stab type |
85 | * Questions:: Questions and anomolies | |
86 | * xcoff-differences:: Differences between GNU stabs in a.out | |
87 | and GNU stabs in xcoff | |
88 | * Sun-differences:: Differences between GNU stabs and Sun | |
89 | native stabs | |
e505224d | 90 | @end menu |
899bafeb | 91 | @end ifinfo |
e505224d PB |
92 | |
93 | ||
899bafeb | 94 | @node Overview |
e505224d PB |
95 | @chapter Overview of stabs |
96 | ||
139741da RP |
97 | @dfn{Stabs} refers to a format for information that describes a program |
98 | to a debugger. This format was apparently invented by | |
99 | @c FIXME! <<name of inventor>> at | |
100 | the University of California at Berkeley, for the @code{pdx} Pascal | |
101 | debugger; the format has spread widely since then. | |
102 | ||
8c59ee11 JK |
103 | This document is one of the few published sources of documentation on |
104 | stabs. It is believed to be completely comprehensive for stabs used by | |
105 | C. The lists of symbol descriptors (@pxref{Symbol Descriptors}) and | |
106 | type descriptors (@pxref{Type Descriptors}) are believed to be completely | |
107 | comprehensive. There are known to be stabs for C++ and COBOL which are | |
108 | poorly documented here. Stabs specific to other languages (e.g. Pascal, | |
109 | Modula-2) are probably not as well documented as they should be. | |
110 | ||
111 | Other sources of information on stabs are @cite{dbx and dbxtool | |
112 | interfaces}, 2nd edition, by Sun, circa 1988, and @cite{AIX Version 3.2 | |
113 | Files Reference}, Fourth Edition, September 1992, "dbx Stabstring | |
114 | Grammar" in the a.out section, page 2-31. This document is believed to | |
115 | incorporate the information from those two sources except where it | |
116 | explictly directs you to them for more information. | |
117 | ||
e505224d PB |
118 | @menu |
119 | * Flow:: Overview of debugging information flow | |
8c59ee11 | 120 | * Stabs Format:: Overview of stab format |
e505224d PB |
121 | * C example:: A simple example in C source |
122 | * Assembly code:: The simple example at the assembly level | |
123 | @end menu | |
124 | ||
899bafeb | 125 | @node Flow |
e505224d PB |
126 | @section Overview of debugging information flow |
127 | ||
139741da RP |
128 | The GNU C compiler compiles C source in a @file{.c} file into assembly |
129 | language in a @file{.s} file, which is translated by the assembler into | |
130 | a @file{.o} file, and then linked with other @file{.o} files and | |
131 | libraries to produce an executable file. | |
e505224d | 132 | |
139741da RP |
133 | With the @samp{-g} option, GCC puts additional debugging information in |
134 | the @file{.s} file, which is slightly transformed by the assembler and | |
e505224d PB |
135 | linker, and carried through into the final executable. This debugging |
136 | information describes features of the source file like line numbers, | |
137 | the types and scopes of variables, and functions, their parameters and | |
138 | their scopes. | |
139 | ||
140 | For some object file formats, the debugging information is | |
139741da | 141 | encapsulated in assembler directives known collectively as `stab' (symbol |
e505224d PB |
142 | table) directives, interspersed with the generated code. Stabs are |
143 | the native format for debugging information in the a.out and xcoff | |
144 | object file formats. The GNU tools can also emit stabs in the coff | |
145 | and ecoff object file formats. | |
146 | ||
139741da RP |
147 | The assembler adds the information from stabs to the symbol information |
148 | it places by default in the symbol table and the string table of the | |
149 | @file{.o} file it is building. The linker consolidates the @file{.o} | |
150 | files into one executable file, with one symbol table and one string | |
151 | table. Debuggers use the symbol and string tables in the executable as | |
152 | a source of debugging information about the program. | |
e505224d | 153 | |
8c59ee11 | 154 | @node Stabs Format |
e505224d PB |
155 | @section Overview of stab format |
156 | ||
157 | There are three overall formats for stab assembler directives | |
139741da RP |
158 | differentiated by the first word of the stab. The name of the directive |
159 | describes what combination of four possible data fields will follow. It | |
160 | is either @code{.stabs} (string), @code{.stabn} (number), or | |
161 | @code{.stabd} (dot). | |
e505224d PB |
162 | |
163 | The overall format of each class of stab is: | |
164 | ||
165 | @example | |
139741da RP |
166 | .stabs "@var{string}",@var{type},0,@var{desc},@var{value} |
167 | .stabn @var{type},0,@var{desc},@var{value} | |
168 | .stabd @var{type},0,@var{desc} | |
e505224d PB |
169 | @end example |
170 | ||
139741da RP |
171 | In general, in @code{.stabs} the @var{string} field contains name and type |
172 | information. For @code{.stabd} the value field is implicit and has the value | |
e505224d PB |
173 | of the current file location. Otherwise the value field often |
174 | contains a relocatable address, frame pointer offset, or register | |
175 | number, that maps to the source code element described by the stab. | |
176 | ||
6897f9ec JK |
177 | The number in the type field gives some basic information about what |
178 | type of stab this is (or whether it @emph{is} a stab, as opposed to an | |
179 | ordinary symbol). Each possible type number defines a different stab | |
180 | type. The stab type further defines the exact interpretation of, and | |
181 | possible values for, any remaining @code{"@var{string}"}, @var{desc}, or | |
139741da | 182 | @var{value} fields present in the stab. Table A (@pxref{Stab |
6897f9ec JK |
183 | types,,Table A: Symbol types from stabs}) lists in numeric order the |
184 | possible type field values for stab directives. The reference section | |
185 | that follows Table A describes the meaning of the fields for each stab | |
186 | type in detail. The examples that follow this overview introduce the | |
187 | stab types in terms of the source code elements they describe. | |
e505224d | 188 | |
139741da RP |
189 | For @code{.stabs} the @code{"@var{string}"} field holds the meat of the |
190 | debugging information. The generally unstructured nature of this field | |
191 | is what makes stabs extensible. For some stab types the string field | |
192 | contains only a name. For other stab types the contents can be a great | |
193 | deal more complex. | |
e505224d | 194 | |
139741da | 195 | The overall format is of the @code{"@var{string}"} field is: |
e505224d PB |
196 | |
197 | @example | |
139741da RP |
198 | "@var{name}@r{[}:@var{symbol_descriptor}@r{]} |
199 | @r{[}@var{type_number}@r{[}=@var{type_descriptor} @r{@dots{}]]}" | |
e505224d PB |
200 | @end example |
201 | ||
139741da | 202 | @var{name} is the name of the symbol represented by the stab. |
6897f9ec | 203 | @var{name} can be omitted, which means the stab represents an unnamed |
8c59ee11 | 204 | object. For example, @samp{:t10=*2} defines type 10 as a pointer to |
6897f9ec JK |
205 | type 2, but does not give the type a name. Omitting the @var{name} |
206 | field is supported by AIX dbx and GDB after about version 4.8, but not | |
207 | other debuggers. | |
e505224d | 208 | |
139741da RP |
209 | The @var{symbol_descriptor} following the @samp{:} is an alphabetic |
210 | character that tells more specifically what kind of symbol the stab | |
211 | represents. If the @var{symbol_descriptor} is omitted, but type | |
212 | information follows, then the stab represents a local variable. For a | |
8c59ee11 | 213 | list of symbol descriptors, see @ref{Symbol Descriptors,,Table C: Symbol |
139741da | 214 | descriptors}. |
e505224d | 215 | |
6897f9ec JK |
216 | The @samp{c} symbol descriptor is an exception in that it is not |
217 | followed by type information. @xref{Constants}. | |
218 | ||
139741da RP |
219 | Type information is either a @var{type_number}, or a |
220 | @samp{@var{type_number}=}. The @var{type_number} alone is a type | |
221 | reference, referring directly to a type that has already been defined. | |
e505224d | 222 | |
139741da RP |
223 | The @samp{@var{type_number}=} is a type definition, where the number |
224 | represents a new type which is about to be defined. The type definition | |
225 | may refer to other types by number, and those type numbers may be | |
226 | followed by @samp{=} and nested definitions. | |
e505224d PB |
227 | |
228 | In a type definition, if the character that follows the equals sign is | |
139741da RP |
229 | non-numeric then it is a @var{type_descriptor}, and tells what kind of |
230 | type is about to be defined. Any other values following the | |
231 | @var{type_descriptor} vary, depending on the @var{type_descriptor}. If | |
232 | a number follows the @samp{=} then the number is a @var{type_reference}. | |
233 | This is described more thoroughly in the section on types. @xref{Type | |
234 | Descriptors,,Table D: Type Descriptors}, for a list of | |
235 | @var{type_descriptor} values. | |
236 | ||
6897f9ec JK |
237 | There is an AIX extension for type attributes. Following the @samp{=} |
238 | is any number of type attributes. Each one starts with @samp{@@} and | |
239 | ends with @samp{;}. Debuggers, including AIX's dbx, skip any type | |
8c59ee11 JK |
240 | attributes they do not recognize. GDB 4.9 does not do this--it will |
241 | ignore the entire symbol containing a type attribute. Hopefully this | |
242 | will be fixed in the next GDB release. Because of a conflict with C++ | |
243 | (@pxref{Cplusplus}), new attributes should not be defined which begin | |
244 | with a digit, @samp{(}, or @samp{-}; GDB may be unable to distinguish | |
245 | those from the C++ type descriptor @samp{@@}. The attributes are: | |
6897f9ec JK |
246 | |
247 | @table @code | |
248 | @item a@var{boundary} | |
8c59ee11 | 249 | @var{boundary} is an integer specifying the alignment. I assume it |
6897f9ec JK |
250 | applies to all variables of this type. |
251 | ||
252 | @item s@var{size} | |
8c59ee11 | 253 | Size in bits of a variable of this type. |
6897f9ec JK |
254 | |
255 | @item p@var{integer} | |
256 | Pointer class (for checking). Not sure what this means, or how | |
257 | @var{integer} is interpreted. | |
258 | ||
259 | @item P | |
260 | Indicate this is a packed type, meaning that structure fields or array | |
261 | elements are placed more closely in memory, to save memory at the | |
262 | expense of speed. | |
263 | @end table | |
264 | ||
b6963343 JK |
265 | All this can make the @code{"@var{string}"} field quite long. All |
266 | versions of GDB, and some versions of DBX, can handle arbitrarily long | |
267 | strings. But many versions of DBX cretinously limit the strings to | |
268 | about 80 characters, so compilers which must work with such DBX's need | |
269 | to split the @code{.stabs} directive into several @code{.stabs} | |
270 | directives. Each stab duplicates exactly all but the | |
6897f9ec | 271 | @code{"@var{string}"} field. The @code{"@var{string}"} field of |
b6963343 JK |
272 | every stab except the last is marked as continued with a |
273 | double-backslash at the end. Removing the backslashes and concatenating | |
274 | the @code{"@var{string}"} fields of each stab produces the original, | |
275 | long string. | |
e505224d | 276 | |
899bafeb | 277 | @node C example |
e505224d PB |
278 | @section A simple example in C source |
279 | ||
280 | To get the flavor of how stabs describe source information for a C | |
281 | program, let's look at the simple program: | |
282 | ||
283 | @example | |
284 | main() | |
285 | @{ | |
139741da | 286 | printf("Hello world"); |
e505224d PB |
287 | @} |
288 | @end example | |
289 | ||
139741da RP |
290 | When compiled with @samp{-g}, the program above yields the following |
291 | @file{.s} file. Line numbers have been added to make it easier to refer | |
292 | to parts of the @file{.s} file in the description of the stabs that | |
293 | follows. | |
e505224d | 294 | |
899bafeb | 295 | @node Assembly code |
e505224d PB |
296 | @section The simple example at the assembly level |
297 | ||
298 | @example | |
299 | 1 gcc2_compiled.: | |
300 | 2 .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 | |
301 | 3 .stabs "hello.c",100,0,0,Ltext0 | |
302 | 4 .text | |
303 | 5 Ltext0: | |
304 | 6 .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 | |
305 | 7 .stabs "char:t2=r2;0;127;",128,0,0,0 | |
306 | 8 .stabs "long int:t3=r1;-2147483648;2147483647;",128,0,0,0 | |
307 | 9 .stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 | |
308 | 10 .stabs "long unsigned int:t5=r1;0;-1;",128,0,0,0 | |
309 | 11 .stabs "short int:t6=r1;-32768;32767;",128,0,0,0 | |
310 | 12 .stabs "long long int:t7=r1;0;-1;",128,0,0,0 | |
311 | 13 .stabs "short unsigned int:t8=r1;0;65535;",128,0,0,0 | |
312 | 14 .stabs "long long unsigned int:t9=r1;0;-1;",128,0,0,0 | |
313 | 15 .stabs "signed char:t10=r1;-128;127;",128,0,0,0 | |
314 | 16 .stabs "unsigned char:t11=r1;0;255;",128,0,0,0 | |
315 | 17 .stabs "float:t12=r1;4;0;",128,0,0,0 | |
316 | 18 .stabs "double:t13=r1;8;0;",128,0,0,0 | |
317 | 19 .stabs "long double:t14=r1;8;0;",128,0,0,0 | |
318 | 20 .stabs "void:t15=15",128,0,0,0 | |
139741da | 319 | 21 .align 4 |
e505224d | 320 | 22 LC0: |
139741da RP |
321 | 23 .ascii "Hello, world!\12\0" |
322 | 24 .align 4 | |
323 | 25 .global _main | |
324 | 26 .proc 1 | |
e505224d PB |
325 | 27 _main: |
326 | 28 .stabn 68,0,4,LM1 | |
327 | 29 LM1: | |
139741da RP |
328 | 30 !#PROLOGUE# 0 |
329 | 31 save %sp,-136,%sp | |
330 | 32 !#PROLOGUE# 1 | |
331 | 33 call ___main,0 | |
332 | 34 nop | |
e505224d PB |
333 | 35 .stabn 68,0,5,LM2 |
334 | 36 LM2: | |
335 | 37 LBB2: | |
139741da RP |
336 | 38 sethi %hi(LC0),%o1 |
337 | 39 or %o1,%lo(LC0),%o0 | |
338 | 40 call _printf,0 | |
339 | 41 nop | |
e505224d PB |
340 | 42 .stabn 68,0,6,LM3 |
341 | 43 LM3: | |
342 | 44 LBE2: | |
343 | 45 .stabn 68,0,6,LM4 | |
344 | 46 LM4: | |
345 | 47 L1: | |
139741da RP |
346 | 48 ret |
347 | 49 restore | |
e505224d PB |
348 | 50 .stabs "main:F1",36,0,0,_main |
349 | 51 .stabn 192,0,0,LBB2 | |
350 | 52 .stabn 224,0,0,LBE2 | |
351 | @end example | |
352 | ||
139741da | 353 | This simple ``hello world'' example demonstrates several of the stab |
e505224d PB |
354 | types used to describe C language source files. |
355 | ||
899bafeb | 356 | @node Program structure |
139741da | 357 | @chapter Encoding for the structure of the program |
e505224d PB |
358 | |
359 | @menu | |
360 | * Source file:: The path and name of the source file | |
361 | * Line numbers:: | |
362 | * Procedures:: | |
8d0dca57 | 363 | * Block Structure:: |
e505224d PB |
364 | @end menu |
365 | ||
899bafeb | 366 | @node Source file |
e505224d PB |
367 | @section The path and name of the source file |
368 | ||
139741da RP |
369 | @table @strong |
370 | @item Directive: | |
371 | @code{.stabs} | |
372 | @item Type: | |
373 | @code{N_SO} | |
374 | @end table | |
e505224d PB |
375 | |
376 | The first stabs in the .s file contain the name and path of the source | |
377 | file that was compiled to produce the .s file. This information is | |
378 | contained in two records of stab type N_SO (100). | |
379 | ||
380 | @example | |
381 | .stabs "path_name", N_SO, NIL, NIL, Code_address_of_program_start | |
382 | .stabs "file_name:", N_SO, NIL, NIL, Code_address_of_program_start | |
383 | @end example | |
384 | ||
385 | @example | |
386 | 2 .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 | |
387 | 3 .stabs "hello.c",100,0,0,Ltext0 | |
139741da | 388 | 4 .text |
e505224d PB |
389 | 5 Ltext0: |
390 | @end example | |
391 | ||
899bafeb | 392 | @node Line numbers |
e505224d PB |
393 | @section Line Numbers |
394 | ||
139741da RP |
395 | @table @strong |
396 | @item Directive: | |
397 | @code{.stabn} | |
398 | @item Type: | |
399 | @code{N_SLINE} | |
400 | @end table | |
e505224d | 401 | |
139741da | 402 | The start of source lines is represented by the @code{N_SLINE} (68) stab |
e505224d PB |
403 | type. |
404 | ||
405 | @example | |
139741da | 406 | .stabn N_SLINE, NIL, @var{line}, @var{address} |
e505224d PB |
407 | @end example |
408 | ||
139741da RP |
409 | @var{line} is a source line number; @var{address} represents the code |
410 | address for the start of that source line. | |
411 | ||
e505224d PB |
412 | @example |
413 | 27 _main: | |
414 | 28 .stabn 68,0,4,LM1 | |
415 | 29 LM1: | |
139741da | 416 | 30 !#PROLOGUE# 0 |
e505224d PB |
417 | @end example |
418 | ||
899bafeb | 419 | @node Procedures |
6897f9ec JK |
420 | @section Procedures |
421 | ||
422 | All of the following stabs use the @samp{N_FUN} symbol type. | |
423 | ||
424 | A function is represented by a @samp{F} symbol descriptor for a global | |
425 | (extern) function, and @samp{f} for a static (local) function. The next | |
426 | @samp{N_SLINE} symbol can be used to find the line number of the start | |
427 | of the function. The value field is the address of the start of the | |
428 | function. The type information of the stab represents the return type | |
429 | of the function; thus @samp{foo:f5} means that foo is a function | |
430 | returning type 5. | |
431 | ||
432 | The AIX documentation also defines symbol descriptor @samp{J} as an | |
433 | internal function. I assume this means a function nested within another | |
434 | function. It also says Symbol descriptor @samp{m} is a module in | |
435 | Modula-2 or extended Pascal. | |
436 | ||
437 | Procedures (functions which do not return values) are represented as | |
438 | functions returning the void type in C. I don't see why this couldn't | |
439 | be used for all languages (inventing a void type for this purpose if | |
440 | necessary), but the AIX documentation defines @samp{I}, @samp{P}, and | |
441 | @samp{Q} for internal, global, and static procedures, respectively. | |
442 | These symbol descriptors are unusual in that they are not followed by | |
443 | type information. | |
444 | ||
8c59ee11 JK |
445 | For any of the above symbol descriptors, after the symbol descriptor and |
446 | the type information, there is optionally a comma, followed by the name | |
447 | of the procedure, followed by a comma, followed by a name specifying the | |
448 | scope. The first name is local to the scope specified. I assume then | |
449 | that the name of the symbol (before the @samp{:}), if specified, is some | |
450 | sort of global name. I assume the name specifying the scope is the name | |
451 | of a function specifying that scope. This feature is an AIX extension, | |
452 | and this information is based on the manual; I haven't actually tried | |
453 | it. | |
6897f9ec JK |
454 | |
455 | The stab representing a procedure is located immediately following the | |
456 | code of the procedure. This stab is in turn directly followed by a | |
457 | group of other stabs describing elements of the procedure. These other | |
458 | stabs describe the procedure's parameters, its block local variables and | |
459 | its block structure. | |
e505224d PB |
460 | |
461 | @example | |
139741da RP |
462 | 48 ret |
463 | 49 restore | |
e505224d PB |
464 | @end example |
465 | ||
139741da RP |
466 | The @code{.stabs} entry after this code fragment shows the @var{name} of |
467 | the procedure (@code{main}); the type descriptor @var{desc} (@code{F}, | |
468 | for a global procedure); a reference to the predefined type @code{int} | |
469 | for the return type; and the starting @var{address} of the procedure. | |
470 | ||
471 | Here is an exploded summary (with whitespace introduced for clarity), | |
472 | followed by line 50 of our sample assembly output, which has this form: | |
473 | ||
e505224d | 474 | @example |
139741da RP |
475 | .stabs "@var{name}: |
476 | @var{desc} @r{(global proc @samp{F})} | |
477 | @var{return_type_ref} @r{(int)} | |
478 | ",N_FUN, NIL, NIL, | |
479 | @var{address} | |
e505224d PB |
480 | @end example |
481 | ||
482 | @example | |
483 | 50 .stabs "main:F1",36,0,0,_main | |
484 | @end example | |
485 | ||
899bafeb | 486 | @node Block Structure |
e505224d PB |
487 | @section Block Structure |
488 | ||
139741da RP |
489 | @table @strong |
490 | @item Directive: | |
491 | @code{.stabn} | |
492 | @item Types: | |
493 | @code{N_LBRAC}, @code{N_RBRAC} | |
494 | @end table | |
e505224d | 495 | |
139741da RP |
496 | The program's block structure is represented by the @code{N_LBRAC} (left |
497 | brace) and the @code{N_RBRAC} (right brace) stab types. The following code | |
498 | range, which is the body of @code{main}, is labeled with @samp{LBB2:} at the | |
499 | beginning and @samp{LBE2:} at the end. | |
e505224d PB |
500 | |
501 | @example | |
502 | 37 LBB2: | |
139741da RP |
503 | 38 sethi %hi(LC0),%o1 |
504 | 39 or %o1,%lo(LC0),%o0 | |
505 | 40 call _printf,0 | |
506 | 41 nop | |
e505224d PB |
507 | 42 .stabn 68,0,6,LM3 |
508 | 43 LM3: | |
509 | 44 LBE2: | |
510 | @end example | |
511 | ||
139741da RP |
512 | The @code{N_LBRAC} and @code{N_RBRAC} stabs that describe the block |
513 | scope of the procedure are located after the @code{N_FUNC} stab that | |
514 | represents the procedure itself. The @code{N_LBRAC} uses the | |
515 | @code{LBB2} label as the code address in its value field, and the | |
516 | @code{N_RBRAC} uses @code{LBE2}. | |
e505224d PB |
517 | |
518 | @example | |
519 | 50 .stabs "main:F1",36,0,0,_main | |
520 | @end example | |
521 | ||
522 | @example | |
139741da RP |
523 | .stabn N_LBRAC, NIL, NIL, @var{left-brace-address} |
524 | .stabn N_RBRAC, NIL, NIL, @var{right-brace-address} | |
e505224d PB |
525 | @end example |
526 | ||
527 | @example | |
528 | 51 .stabn 192,0,0,LBB2 | |
529 | 52 .stabn 224,0,0,LBE2 | |
530 | @end example | |
531 | ||
6897f9ec JK |
532 | @node Constants |
533 | @chapter Constants | |
534 | ||
535 | The @samp{c} symbol descriptor indicates that this stab represents a | |
536 | constant. This symbol descriptor is an exception to the general rule | |
537 | that symbol descriptors are followed by type information. Instead, it | |
538 | is followed by @samp{=} and one of the following: | |
539 | ||
540 | @table @code | |
541 | @item b@var{value} | |
542 | Boolean constant. @var{value} is a numeric value; I assume it is 0 for | |
543 | false or 1 for true. | |
544 | ||
545 | @item c@var{value} | |
546 | Character constant. @var{value} is the numeric value of the constant. | |
547 | ||
548 | @item e@var{type-information},@var{value} | |
549 | Enumeration constant. @var{type-information} is the type of the | |
550 | constant, as it would appear after a symbol descriptor | |
8c59ee11 | 551 | (@pxref{Stabs Format}). @var{value} is the numeric value of the constant. |
6897f9ec JK |
552 | |
553 | @item i@var{value} | |
554 | Integer constant. @var{value} is the numeric value. | |
555 | ||
556 | @item r@var{value} | |
557 | Real constant. @var{value} is the real value, which can be @samp{INF} | |
558 | (optionally preceded by a sign) for infinity, @samp{QNAN} for a quiet | |
559 | NaN (not-a-number), or @samp{SNAN} for a signalling NaN. If it is a | |
560 | normal number the format is that accepted by the C library function | |
561 | @code{atof}. | |
562 | ||
563 | @item s@var{string} | |
564 | String constant. @var{string} is a string enclosed in either @samp{'} | |
565 | (in which case @samp{'} characters within the string are represented as | |
566 | @samp{\'} or @samp{"} (in which case @samp{"} characters within the | |
567 | string are represented as @samp{\"}). | |
568 | ||
569 | @item S@var{type-information},@var{elements},@var{bits},@var{pattern} | |
570 | Set constant. @var{type-information} is the type of the constant, as it | |
8c59ee11 | 571 | would appear after a symbol descriptor (@pxref{Stabs Format}). |
6897f9ec JK |
572 | @var{elements} is the number of elements in the set (is this just the |
573 | number of bits set in @var{pattern}? Or redundant with the type? I | |
574 | don't get it), @var{bits} is the number of bits in the constant (meaning | |
575 | it specifies the length of @var{pattern}, I think), and @var{pattern} is | |
576 | a hexadecimal representation of the set. AIX documentation refers to a | |
577 | limit of 32 bytes, but I see no reason why this limit should exist. | |
578 | @end table | |
579 | ||
580 | The boolean, character, string, and set constants are not supported by | |
581 | GDB 4.9, but it will ignore them. GDB 4.8 and earlier gave an error | |
582 | message and refused to read symbols from the file containing the | |
583 | constants. | |
584 | ||
585 | This information is followed by @samp{;}. | |
586 | ||
899bafeb | 587 | @node Example |
e505224d PB |
588 | @chapter A Comprehensive Example in C |
589 | ||
139741da | 590 | Now we'll examine a second program, @code{example2}, which builds on the |
e505224d PB |
591 | first example to introduce the rest of the stab types, symbol |
592 | descriptors, and type descriptors used in C. | |
139741da RP |
593 | @xref{Example2.c} for the complete @file{.c} source, |
594 | and @pxref{Example2.s} for the @file{.s} assembly code. | |
e505224d PB |
595 | This description includes parts of those files. |
596 | ||
597 | @section Flow of control and nested scopes | |
598 | ||
9cd64d11 | 599 | @table @strong |
139741da RP |
600 | @item Directive: |
601 | @code{.stabn} | |
602 | @item Types: | |
603 | @code{N_SLINE}, @code{N_LBRAC}, @code{N_RBRAC} (cont.) | |
604 | @end table | |
e505224d | 605 | |
899bafeb RP |
606 | Consider the body of @code{main}, from @file{example2.c}. It shows more |
607 | about how @code{N_SLINE}, @code{N_RBRAC}, and @code{N_LBRAC} stabs are used. | |
e505224d PB |
608 | |
609 | @example | |
610 | 20 @{ | |
611 | 21 static float s_flap; | |
139741da RP |
612 | 22 int times; |
613 | 23 for (times=0; times < s_g_repeat; times++)@{ | |
614 | 24 int inner; | |
615 | 25 printf ("Hello world\n"); | |
616 | 26 @} | |
e505224d PB |
617 | 27 @}; |
618 | @end example | |
619 | ||
899bafeb | 620 | Here we have a single source line, the @samp{for} line, that generates |
e505224d | 621 | non-linear flow of control, and non-contiguous code. In this case, an |
899bafeb | 622 | @code{N_SLINE} stab with the same line number proceeds each block of |
e505224d PB |
623 | non-contiguous code generated from the same source line. |
624 | ||
139741da RP |
625 | The example also shows nested scopes. The @code{N_LBRAC} and |
626 | @code{N_LBRAC} stabs that describe block structure are nested in the | |
627 | same order as the corresponding code blocks, those of the for loop | |
628 | inside those for the body of main. | |
e505224d | 629 | |
139741da RP |
630 | @noindent |
631 | This is the label for the @code{N_LBRAC} (left brace) stab marking the | |
632 | start of @code{main}. | |
e505224d | 633 | |
139741da | 634 | @example |
e505224d | 635 | 57 LBB2: |
139741da RP |
636 | @end example |
637 | ||
638 | @noindent | |
639 | In the first code range for C source line 23, the @code{for} loop | |
640 | initialize and test, @code{N_SLINE} (68) records the line number: | |
e505224d | 641 | |
139741da RP |
642 | @example |
643 | .stabn N_SLINE, NIL, | |
644 | @var{line}, | |
645 | @var{address} | |
e505224d | 646 | |
e505224d PB |
647 | 58 .stabn 68,0,23,LM2 |
648 | 59 LM2: | |
139741da | 649 | 60 st %g0,[%fp-20] |
e505224d | 650 | 61 L2: |
139741da RP |
651 | 62 sethi %hi(_s_g_repeat),%o0 |
652 | 63 ld [%fp-20],%o1 | |
653 | 64 ld [%o0+%lo(_s_g_repeat)],%o0 | |
654 | 65 cmp %o1,%o0 | |
655 | 66 bge L3 | |
656 | 67 nop | |
e505224d | 657 | |
139741da | 658 | @exdent label for the @code{N_LBRAC} (start block) marking the start of @code{for} loop |
e505224d | 659 | |
e505224d PB |
660 | 68 LBB3: |
661 | 69 .stabn 68,0,25,LM3 | |
662 | 70 LM3: | |
139741da RP |
663 | 71 sethi %hi(LC0),%o1 |
664 | 72 or %o1,%lo(LC0),%o0 | |
665 | 73 call _printf,0 | |
666 | 74 nop | |
e505224d PB |
667 | 75 .stabn 68,0,26,LM4 |
668 | 76 LM4: | |
e505224d | 669 | |
139741da | 670 | @exdent label for the @code{N_RBRAC} (end block) stab marking the end of the @code{for} loop |
e505224d | 671 | |
e505224d | 672 | 77 LBE3: |
139741da | 673 | @end example |
e505224d | 674 | |
139741da RP |
675 | @noindent |
676 | Now we come to the second code range for source line 23, the @code{for} | |
677 | loop increment and return. Once again, @code{N_SLINE} (68) records the | |
678 | source line number: | |
612dbd4c | 679 | |
139741da RP |
680 | @example |
681 | .stabn, N_SLINE, NIL, | |
682 | @var{line}, | |
683 | @var{address} | |
e505224d | 684 | |
e505224d PB |
685 | 78 .stabn 68,0,23,LM5 |
686 | 79 LM5: | |
687 | 80 L4: | |
139741da RP |
688 | 81 ld [%fp-20],%o0 |
689 | 82 add %o0,1,%o1 | |
690 | 83 st %o1,[%fp-20] | |
691 | 84 b,a L2 | |
e505224d PB |
692 | 85 L3: |
693 | 86 .stabn 68,0,27,LM6 | |
694 | 87 LM6: | |
e505224d | 695 | |
139741da | 696 | @exdent label for the @code{N_RBRAC} (end block) stab marking the end of the @code{for} loop |
e505224d | 697 | |
e505224d PB |
698 | 88 LBE2: |
699 | 89 .stabn 68,0,27,LM7 | |
700 | 90 LM7: | |
701 | 91 L1: | |
139741da RP |
702 | 92 ret |
703 | 93 restore | |
e505224d PB |
704 | 94 .stabs "main:F1",36,0,0,_main |
705 | 95 .stabs "argc:p1",160,0,0,68 | |
706 | 96 .stabs "argv:p20=*21=*2",160,0,0,72 | |
707 | 97 .stabs "s_flap:V12",40,0,0,_s_flap.0 | |
708 | 98 .stabs "times:1",128,0,0,-20 | |
139741da RP |
709 | @end example |
710 | ||
711 | @noindent | |
712 | Here is an illustration of stabs describing nested scopes. The scope | |
713 | nesting is reflected in the nested bracketing stabs (@code{N_LBRAC}, | |
714 | 192, appears here). | |
e505224d | 715 | |
139741da RP |
716 | @example |
717 | .stabn N_LBRAC,NIL,NIL, | |
718 | @var{block-start-address} | |
e505224d PB |
719 | |
720 | 99 .stabn 192,0,0,LBB2 ## begin proc label | |
721 | 100 .stabs "inner:1",128,0,0,-24 | |
722 | 101 .stabn 192,0,0,LBB3 ## begin for label | |
139741da | 723 | @end example |
e505224d | 724 | |
139741da RP |
725 | @noindent |
726 | @code{N_RBRAC} (224), ``right brace'' ends a lexical block (scope). | |
727 | ||
728 | @example | |
729 | .stabn N_RBRAC,NIL,NIL, | |
730 | @var{block-end-address} | |
e505224d PB |
731 | |
732 | 102 .stabn 224,0,0,LBE3 ## end for label | |
733 | 103 .stabn 224,0,0,LBE2 ## end proc label | |
734 | @end example | |
735 | ||
899bafeb | 736 | @node Variables |
e505224d PB |
737 | @chapter Variables |
738 | ||
739 | @menu | |
740 | * Automatic variables:: locally scoped | |
8d0dca57 | 741 | * Global Variables:: |
e505224d PB |
742 | * Register variables:: |
743 | * Initialized statics:: | |
744 | * Un-initialized statics:: | |
745 | * Parameters:: | |
746 | @end menu | |
747 | ||
899bafeb | 748 | @node Automatic variables |
e505224d PB |
749 | @section Locally scoped automatic variables |
750 | ||
139741da RP |
751 | @table @strong |
752 | @item Directive: | |
753 | @code{.stabs} | |
754 | @item Type: | |
755 | @code{N_LSYM} | |
756 | @item Symbol Descriptor: | |
757 | none | |
758 | @end table | |
e505224d | 759 | |
139741da RP |
760 | In addition to describing types, the @code{N_LSYM} stab type also |
761 | describes locally scoped automatic variables. Refer again to the body | |
762 | of @code{main} in @file{example2.c}. It allocates two automatic | |
763 | variables: @samp{times} is scoped to the body of @code{main}, and | |
764 | @samp{inner} is scoped to the body of the @code{for} loop. | |
765 | @samp{s_flap} is locally scoped but not automatic, and will be discussed | |
766 | later. | |
e505224d PB |
767 | |
768 | @example | |
769 | 20 @{ | |
770 | 21 static float s_flap; | |
139741da RP |
771 | 22 int times; |
772 | 23 for (times=0; times < s_g_repeat; times++)@{ | |
773 | 24 int inner; | |
774 | 25 printf ("Hello world\n"); | |
775 | 26 @} | |
e505224d PB |
776 | 27 @}; |
777 | @end example | |
778 | ||
139741da RP |
779 | The @code{N_LSYM} stab for an automatic variable is located just before the |
780 | @code{N_LBRAC} stab describing the open brace of the block to which it is | |
e505224d PB |
781 | scoped. |
782 | ||
783 | @example | |
139741da RP |
784 | @exdent @code{N_LSYM} (128): automatic variable, scoped locally to @code{main} |
785 | ||
786 | .stabs "@var{name}: | |
8c59ee11 | 787 | @var{type information}", |
139741da RP |
788 | N_LSYM, NIL, NIL, |
789 | @var{frame-pointer-offset} | |
e505224d PB |
790 | |
791 | 98 .stabs "times:1",128,0,0,-20 | |
792 | 99 .stabn 192,0,0,LBB2 ## begin `main' N_LBRAC | |
793 | ||
139741da RP |
794 | @exdent @code{N_LSYM} (128): automatic variable, scoped locally to the @code{for} loop |
795 | ||
796 | .stabs "@var{name}: | |
8c59ee11 | 797 | @var{type information}", |
139741da RP |
798 | N_LSYM, NIL, NIL, |
799 | @var{frame-pointer-offset} | |
e505224d PB |
800 | |
801 | 100 .stabs "inner:1",128,0,0,-24 | |
802 | 101 .stabn 192,0,0,LBB3 ## begin `for' loop N_LBRAC | |
803 | @end example | |
804 | ||
8c59ee11 JK |
805 | The symbol descriptor is omitted for automatic variables. Since type |
806 | information should being with a digit, @samp{-}, or @samp{(}, only | |
807 | digits, @samp{-}, and @samp{(} are precluded from being used for symbol | |
808 | descriptors by this fact. However, the Acorn RISC machine (ARM) is said | |
809 | to get this wrong: it puts out a mere type definition here, without the | |
810 | preceding @code{@var{typenumber}=}. This is a bad idea; there is no | |
811 | guarantee that type descriptors are distinct from symbol descriptors. | |
e505224d | 812 | |
899bafeb | 813 | @node Global Variables |
e505224d PB |
814 | @section Global Variables |
815 | ||
139741da RP |
816 | @table @strong |
817 | @item Directive: | |
818 | @code{.stabs} | |
819 | @item Type: | |
820 | @code{N_GSYM} | |
821 | @item Symbol Descriptor: | |
822 | @code{G} | |
823 | @end table | |
e505224d | 824 | |
139741da RP |
825 | Global variables are represented by the @code{N_GSYM} stab type. The symbol |
826 | descriptor, following the colon in the string field, is @samp{G}. Following | |
827 | the @samp{G} is a type reference or type definition. In this example it is a | |
828 | type reference to the basic C type, @code{char}. The first source line in | |
829 | @file{example2.c}, | |
e505224d PB |
830 | |
831 | @example | |
832 | 1 char g_foo = 'c'; | |
833 | @end example | |
834 | ||
139741da RP |
835 | @noindent |
836 | yields the following stab. The stab immediately precedes the code that | |
e505224d PB |
837 | allocates storage for the variable it describes. |
838 | ||
839 | @example | |
139741da RP |
840 | @exdent @code{N_GSYM} (32): global symbol |
841 | ||
842 | .stabs "@var{name}: | |
843 | @var{descriptor} | |
844 | @var{type-ref}", | |
845 | N_GSYM, NIL, NIL, NIL | |
e505224d | 846 | |
e505224d | 847 | 21 .stabs "g_foo:G2",32,0,0,0 |
139741da RP |
848 | 22 .global _g_foo |
849 | 23 .data | |
e505224d | 850 | 24 _g_foo: |
139741da | 851 | 25 .byte 99 |
e505224d PB |
852 | @end example |
853 | ||
139741da RP |
854 | The address of the variable represented by the @code{N_GSYM} is not contained |
855 | in the @code{N_GSYM} stab. The debugger gets this information from the | |
e505224d PB |
856 | external symbol for the global variable. |
857 | ||
899bafeb | 858 | @node Register variables |
6897f9ec | 859 | @section Register variables |
139741da | 860 | |
8c59ee11 JK |
861 | @c According to an old version of this manual, AIX uses C_RPSYM instead |
862 | @c of C_RSYM. I am skeptical; this should be verified. | |
6897f9ec JK |
863 | Register variables have their own stab type, @code{N_RSYM}, and their |
864 | own symbol descriptor, @code{r}. The stab's value field contains the | |
865 | number of the register where the variable data will be stored. | |
e505224d | 866 | |
6897f9ec | 867 | The value is the register number. |
e505224d | 868 | |
6897f9ec JK |
869 | AIX defines a separate symbol descriptor @samp{d} for floating point |
870 | registers. This seems incredibly stupid--why not just just give | |
8c59ee11 JK |
871 | floating point registers different register numbers? I have not |
872 | verified whether the compiler actually uses @samp{d}. | |
e505224d | 873 | |
6897f9ec JK |
874 | If the register is explicitly allocated to a global variable, but not |
875 | initialized, as in | |
e505224d PB |
876 | |
877 | @example | |
6897f9ec | 878 | register int g_bar asm ("%g5"); |
e505224d PB |
879 | @end example |
880 | ||
6897f9ec JK |
881 | the stab may be emitted at the end of the object file, with |
882 | the other bss symbols. | |
e505224d | 883 | |
899bafeb | 884 | @node Initialized statics |
e505224d PB |
885 | @section Initialized static variables |
886 | ||
139741da RP |
887 | @table @strong |
888 | @item Directive: | |
889 | @code{.stabs} | |
890 | @item Type: | |
891 | @code{N_STSYM} | |
892 | @item Symbol Descriptors: | |
893 | @code{S} (file scope), @code{V} (procedure scope) | |
894 | @end table | |
e505224d | 895 | |
139741da RP |
896 | Initialized static variables are represented by the @code{N_STSYM} stab |
897 | type. The symbol descriptor part of the string field shows if the | |
898 | variable is file scope static (@samp{S}) or procedure scope static | |
899 | (@samp{V}). The source line | |
e505224d PB |
900 | |
901 | @example | |
902 | 3 static int s_g_repeat = 2; | |
903 | @end example | |
904 | ||
139741da RP |
905 | @noindent |
906 | yields the following code. The stab is located immediately preceding | |
e505224d | 907 | the storage for the variable it represents. Since the variable in |
139741da | 908 | this example is file scope static the symbol descriptor is @samp{S}. |
e505224d PB |
909 | |
910 | @example | |
139741da RP |
911 | @exdent @code{N_STSYM} (38): initialized static variable (data seg w/internal linkage) |
912 | ||
913 | .stabs "@var{name}: | |
914 | @var{descriptor} | |
915 | @var{type-ref}", | |
916 | N_STSYM,NIL,NIL, | |
917 | @var{address} | |
918 | ||
e505224d | 919 | 26 .stabs "s_g_repeat:S1",38,0,0,_s_g_repeat |
139741da | 920 | 27 .align 4 |
e505224d | 921 | 28 _s_g_repeat: |
139741da | 922 | 29 .word 2 |
e505224d PB |
923 | @end example |
924 | ||
925 | ||
899bafeb | 926 | @node Un-initialized statics |
e505224d PB |
927 | @section Un-initialized static variables |
928 | ||
139741da RP |
929 | @table @strong |
930 | @item Directive: | |
931 | @code{.stabs} | |
932 | @item Type: | |
933 | @code{N_LCSYM} | |
934 | @item Symbol Descriptors: | |
935 | @code{S} (file scope), @code{V} (procedure scope) | |
936 | @end table | |
e505224d | 937 | |
139741da RP |
938 | Un-initialized static variables are represented by the @code{N_LCSYM} |
939 | stab type. The symbol descriptor part of the string shows if the | |
940 | variable is file scope static (@samp{S}) or procedure scope static | |
941 | (@samp{V}). In this example it is procedure scope static. The source | |
942 | line allocating @code{s_flap} immediately follows the open brace for the | |
943 | procedure @code{main}. | |
e505224d PB |
944 | |
945 | @example | |
946 | 20 @{ | |
947 | 21 static float s_flap; | |
948 | @end example | |
949 | ||
139741da RP |
950 | The code that reserves storage for the variable @code{s_flap} precedes the |
951 | body of body of @code{main}. | |
e505224d PB |
952 | |
953 | @example | |
139741da | 954 | 39 .reserve _s_flap.0,4,"bss",4 |
e505224d PB |
955 | @end example |
956 | ||
139741da RP |
957 | But since @code{s_flap} is scoped locally to @code{main}, its stab is |
958 | located with the other stabs representing symbols local to @code{main}. | |
959 | The stab for @code{s_flap} is located just before the @code{N_LBRAC} for | |
960 | @code{main}. | |
e505224d PB |
961 | |
962 | @example | |
139741da RP |
963 | @exdent @code{N_LCSYM} (40): uninitialized static var (BSS seg w/internal linkage) |
964 | ||
965 | .stabs "@var{name}: | |
966 | @var{descriptor} | |
967 | @var{type-ref}", | |
968 | N_LCSYM, NIL, NIL, | |
969 | @var{address} | |
e505224d | 970 | |
e505224d PB |
971 | 97 .stabs "s_flap:V12",40,0,0,_s_flap.0 |
972 | 98 .stabs "times:1",128,0,0,-20 | |
139741da | 973 | 99 .stabn 192,0,0,LBB2 # N_LBRAC for main. |
e505224d PB |
974 | @end example |
975 | ||
139741da RP |
976 | @c ............................................................ |
977 | ||
899bafeb | 978 | @node Parameters |
e505224d PB |
979 | @section Parameters |
980 | ||
497e44a5 | 981 | The symbol descriptor @samp{p} is used to refer to parameters which are |
b82ea042 JK |
982 | in the arglist. Symbols have symbol type @samp{N_PSYM}. The value of |
983 | the symbol is the offset relative to the argument list. | |
984 | ||
985 | If the parameter is passed in a register, then the traditional way to do | |
497e44a5 | 986 | this is to provide two symbols for each argument: |
e505224d PB |
987 | |
988 | @example | |
b82ea042 JK |
989 | .stabs "arg:p1" . . . ; N_PSYM |
990 | .stabs "arg:r1" . . . ; N_RSYM | |
e505224d PB |
991 | @end example |
992 | ||
497e44a5 JK |
993 | Debuggers are expected to use the second one to find the value, and the |
994 | first one to know that it is an argument. | |
e505224d | 995 | |
b82ea042 JK |
996 | Because this is kind of ugly, some compilers use symbol descriptor |
997 | @samp{P} or @samp{R} to indicate an argument which is in a register. | |
998 | The symbol value is the register number. @samp{P} and @samp{R} mean the | |
999 | same thing, the difference is that @samp{P} is a GNU invention and | |
1000 | @samp{R} is an IBM (xcoff) invention. As of version 4.9, GDB should | |
1001 | handle either one. Symbol type @samp{C_RPSYM} is used with @samp{R} and | |
1002 | @samp{N_RSYM} is used with @samp{P}. | |
1003 | ||
6897f9ec JK |
1004 | AIX, according to the documentation, uses @samp{D} for a parameter |
1005 | passed in a floating point register. This strikes me as incredibly | |
1006 | bogus---why doesn't it just use @samp{R} with a register number which | |
23aed449 | 1007 | indicates that it's a floating point register? I haven't verified |
6897f9ec JK |
1008 | whether the system actually does what the documentation indicates. |
1009 | ||
a2a2eac8 JK |
1010 | There is at least one case where GCC uses a @samp{p}/@samp{r} pair |
1011 | rather than @samp{P}; this is where the argument is passed in the | |
1012 | argument list and then loaded into a register. | |
1013 | ||
c156f3c1 JK |
1014 | On the sparc and hppa, for a @samp{P} symbol whose type is a structure |
1015 | or union, the register contains the address of the structure. On the | |
1016 | sparc, this is also true of a @samp{p}/@samp{r} pair (using Sun cc) or a | |
1017 | @samp{p} symbol. However, if a (small) structure is really in a | |
1018 | register, @samp{r} is used. And, to top it all off, on the hppa it | |
1019 | might be a structure which was passed on the stack and loaded into a | |
1020 | register and for which there is a @samp{p}/@samp{r} pair! I believe | |
6897f9ec JK |
1021 | that symbol descriptor @samp{i} is supposed to deal with this case, (it |
1022 | is said to mean "value parameter by reference, indirect access", I don't | |
1023 | know the source for this information) but I don't know details or what | |
1024 | compilers or debuggers use it, if any (not GDB or GCC). It is not clear | |
1025 | to me whether this case needs to be dealt with differently than | |
1026 | parameters passed by reference (see below). | |
c156f3c1 | 1027 | |
b82ea042 | 1028 | There is another case similar to an argument in a register, which is an |
98ef6f31 JK |
1029 | argument which is actually stored as a local variable. Sometimes this |
1030 | happens when the argument was passed in a register and then the compiler | |
1031 | stores it as a local variable. If possible, the compiler should claim | |
1032 | that it's in a register, but this isn't always done. Some compilers use | |
1033 | the pair of symbols approach described above ("arg:p" followed by | |
1034 | "arg:"); this includes gcc1 (not gcc2) on the sparc when passing a small | |
23aed449 JK |
1035 | structure and gcc2 (sometimes) when the argument type is float and it is |
1036 | passed as a double and converted to float by the prologue (in the latter | |
1037 | case the type of the "arg:p" symbol is double and the type of the "arg:" | |
1038 | symbol is float). GCC, at least on the 960, uses a single @samp{p} | |
1039 | symbol descriptor for an argument which is stored as a local variable | |
1040 | but uses @samp{N_LSYM} instead of @samp{N_PSYM}. In this case the value | |
1041 | of the symbol is an offset relative to the local variables for that | |
1042 | function, not relative to the arguments (on some machines those are the | |
1043 | same thing, but not on all). | |
e505224d | 1044 | |
6897f9ec JK |
1045 | If the parameter is passed by reference (e.g. Pascal VAR parameters), |
1046 | then type symbol descriptor is @samp{v} if it is in the argument list, | |
1047 | or @samp{a} if it in a register. Other than the fact that these contain | |
1048 | the address of the parameter other than the parameter itself, they are | |
1049 | identical to @samp{p} and @samp{R}, respectively. I believe @samp{a} is | |
1050 | an AIX invention; @samp{v} is supported by all stabs-using systems as | |
1051 | far as I know. | |
1052 | ||
1053 | @c Is this paragraph correct? It is based on piecing together patchy | |
1054 | @c information and some guesswork | |
1055 | Conformant arrays refer to a feature of Modula-2, and perhaps other | |
1056 | languages, in which the size of an array parameter is not known to the | |
1057 | called function until run-time. Such parameters have two stabs, a | |
1058 | @samp{x} for the array itself, and a @samp{C}, which represents the size | |
1059 | of the array. The value of the @samp{x} stab is the offset in the | |
1060 | argument list where the address of the array is stored (it this right? | |
1061 | it is a guess); the value of the @samp{C} stab is the offset in the | |
1062 | argument list where the size of the array (in elements? in bytes?) is | |
1063 | stored. | |
1064 | ||
1065 | The following are also said to go with @samp{N_PSYM}: | |
a2a2eac8 JK |
1066 | |
1067 | @example | |
1068 | "name" -> "param_name:#type" | |
a2a2eac8 | 1069 | -> pP (<<??>>) |
8c59ee11 | 1070 | -> pF FORTRAN function parameter |
a2a2eac8 JK |
1071 | -> X (function result variable) |
1072 | -> b (based variable) | |
1073 | ||
1074 | value -> offset from the argument pointer (positive). | |
1075 | @end example | |
1076 | ||
497e44a5 | 1077 | As a simple example, the code |
899bafeb | 1078 | |
497e44a5 | 1079 | @example |
b82ea042 JK |
1080 | main (argc, argv) |
1081 | int argc; | |
1082 | char **argv; | |
1083 | @{ | |
497e44a5 JK |
1084 | @end example |
1085 | ||
1086 | produces the stabs | |
899bafeb | 1087 | |
497e44a5 | 1088 | @example |
b82ea042 JK |
1089 | .stabs "main:F1",36,0,0,_main ; 36 is N_FUN |
1090 | .stabs "argc:p1",160,0,0,68 ; 160 is N_PSYM | |
1091 | .stabs "argv:p20=*21=*2",160,0,0,72 | |
e505224d PB |
1092 | @end example |
1093 | ||
497e44a5 | 1094 | The type definition of argv is interesting because it contains several |
a2a2eac8 JK |
1095 | type definitions. Type 21 is pointer to type 2 (char) and argv (type 20) is |
1096 | pointer to type 21. | |
e505224d | 1097 | |
8c59ee11 JK |
1098 | @node Types |
1099 | @chapter Type definitions | |
e505224d | 1100 | |
612dbd4c | 1101 | Now let's look at some variable definitions involving complex types. |
e505224d PB |
1102 | This involves understanding better how types are described. In the |
1103 | examples so far types have been described as references to previously | |
1104 | defined types or defined in terms of subranges of or pointers to | |
1105 | previously defined types. The section that follows will talk about | |
1106 | the various other type descriptors that may follow the = sign in a | |
1107 | type definition. | |
1108 | ||
1109 | @menu | |
8c59ee11 JK |
1110 | * Builtin types:: Integers, floating point, void, etc. |
1111 | * Miscellaneous Types:: Pointers, sets, files, etc. | |
1112 | * Cross-references:: Referring to a type not yet defined. | |
1113 | * Subranges:: A type with a specific range. | |
1114 | * Arrays:: An aggregate type of same-typed elements. | |
1115 | * Strings:: Like an array but also has a length. | |
1116 | * Enumerations:: Like an integer but the values have names. | |
1117 | * Structures:: An aggregate type of different-typed elements. | |
1118 | * Typedefs:: Giving a type a name | |
e505224d PB |
1119 | * Unions:: |
1120 | * Function types:: | |
1121 | @end menu | |
1122 | ||
8c59ee11 JK |
1123 | @node Builtin types |
1124 | @section Builtin types | |
e505224d | 1125 | |
8c59ee11 JK |
1126 | Certain types are built in (@code{int}, @code{short}, @code{void}, |
1127 | @code{float}, etc.); the debugger recognizes these types and knows how | |
1128 | to handle them. Thus don't be surprised if some of the following ways | |
1129 | of specifying builtin types do not specify everything that a debugger | |
1130 | would need to know about the type---in some cases they merely specify | |
1131 | enough information to distinguish the type from other types. | |
1132 | ||
1133 | The traditional way to define builtin types is convolunted, so new ways | |
1134 | have been invented to describe them. Sun's ACC uses the @samp{b} and | |
1135 | @samp{R} type descriptors, and IBM uses negative type numbers. GDB can | |
1136 | accept all three, as of version 4.8; dbx just accepts the traditional | |
1137 | builtin types and perhaps one of the other two formats. | |
1138 | ||
1139 | @menu | |
1140 | * Traditional Builtin Types:: Put on your seatbelts and prepare for kludgery | |
1141 | * Builtin Type Descriptors:: Builtin types with special type descriptors | |
1142 | * Negative Type Numbers:: Builtin types using negative type numbers | |
1143 | @end menu | |
1144 | ||
1145 | @node Traditional Builtin Types | |
1146 | @subsection Traditional Builtin types | |
1147 | ||
1148 | Often types are defined as subranges of themselves. If the array bounds | |
1149 | can fit within an @code{int}, then they are given normally. For example: | |
1150 | ||
1151 | @example | |
1152 | .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 ; 128 is N_LSYM | |
1153 | .stabs "char:t2=r2;0;127;",128,0,0,0 | |
1154 | @end example | |
1155 | ||
1156 | Builtin types can also be described as subranges of @code{int}: | |
1157 | ||
1158 | @example | |
1159 | .stabs "unsigned short:t6=r1;0;65535;",128,0,0,0 | |
1160 | @end example | |
1161 | ||
1162 | If the upper bound of a subrange is -1, it means that the type is an | |
1163 | integral type whose bounds are too big to describe in an int. | |
1164 | Traditionally this is only used for @code{unsigned int} and | |
1165 | @code{unsigned long}; GCC also uses it for @code{long long} and | |
1166 | @code{unsigned long long}, and the only way to tell those types apart is | |
1167 | to look at their names. On other machines GCC puts out bounds in octal, | |
1168 | with a leading 0. In this case a negative bound consists of a number | |
1169 | which is a 1 bit followed by a bunch of 0 bits, and a positive bound is | |
1170 | one in which a bunch of bits are 1. | |
1171 | ||
1172 | @example | |
1173 | .stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 | |
1174 | .stabs "long long int:t7=r1;0;-1;",128,0,0,0 | |
1175 | @end example | |
1176 | ||
1177 | If the upper bound of a subrange is 0, it means that this is a floating | |
1178 | point type, and the lower bound of the subrange indicates the number of | |
1179 | bytes in the type: | |
1180 | ||
1181 | @example | |
1182 | .stabs "float:t12=r1;4;0;",128,0,0,0 | |
1183 | .stabs "double:t13=r1;8;0;",128,0,0,0 | |
1184 | @end example | |
1185 | ||
1186 | However, GCC writes @code{long double} the same way it writes | |
1187 | @code{double}; the only way to distinguish them is by the name: | |
1188 | ||
1189 | @example | |
1190 | .stabs "long double:t14=r1;8;0;",128,0,0,0 | |
1191 | @end example | |
1192 | ||
1193 | Complex types are defined the same way as floating-point types; the only | |
1194 | way to distinguish a single-precision complex from a double-precision | |
1195 | floating-point type is by the name. | |
1196 | ||
1197 | The C @code{void} type is defined as itself: | |
1198 | ||
1199 | @example | |
1200 | .stabs "void:t15=15",128,0,0,0 | |
1201 | @end example | |
1202 | ||
1203 | I'm not sure how a boolean type is represented. | |
1204 | ||
1205 | @node Builtin Type Descriptors | |
1206 | @subsection Defining Builtin Types using Builtin Type Descriptors | |
1207 | ||
1208 | There are various type descriptors to define builtin types: | |
1209 | ||
1210 | @table @code | |
1a8b5668 JK |
1211 | @c FIXME: clean up description of width and offset, once we figure out |
1212 | @c what they mean | |
8c59ee11 JK |
1213 | @item b @var{signed} @var{char-flag} @var{width} ; @var{offset} ; @var{nbits} ; |
1214 | Define an integral type. @var{signed} is @samp{u} for unsigned or | |
1215 | @samp{s} for signed. @var{char-flag} is @samp{c} which indicates this | |
1216 | is a character type, or is omitted. I assume this is to distinguish an | |
1217 | integral type from a character type of the same size, for example it | |
1218 | might make sense to set it for the C type @code{wchar_t} so the debugger | |
1219 | can print such variables differently (Solaris does not do this). Sun | |
1220 | sets it on the C types @code{signed char} and @code{unsigned char} which | |
1221 | arguably is wrong. @var{width} and @var{offset} appear to be for small | |
1222 | objects stored in larger ones, for example a @code{short} in an | |
1223 | @code{int} register. @var{width} is normally the number of bytes in the | |
1224 | type. @var{offset} seems to always be zero. @var{nbits} is the number | |
1225 | of bits in the type. | |
1226 | ||
1227 | Note that type descriptor @samp{b} used for builtin types conflicts with | |
1228 | its use for Pascal space types (@pxref{Miscellaneous Types}); they can | |
1229 | be distinguished because the character following the type descriptor | |
1230 | will be a digit, @samp{(}, or @samp{-} for a Pascal space type, or | |
1231 | @samp{u} or @samp{s} for a builtin type. | |
1232 | ||
1233 | @item w | |
1234 | Documented by AIX to define a wide character type, but their compiler | |
1235 | actually uses negative type numbers (@pxref{Negative Type Numbers}). | |
1236 | ||
1a8b5668 JK |
1237 | @item R @var{fp_type} ; @var{bytes} ; |
1238 | Define a floating point type. @var{fp_type} has one of the following values: | |
1239 | ||
1240 | @table @code | |
1241 | @item 1 (NF_SINGLE) | |
1242 | IEEE 32-bit (single precision) floating point format. | |
1243 | ||
1244 | @item 2 (NF_DOUBLE) | |
1245 | IEEE 64-bit (double precision) floating point format. | |
1246 | ||
1247 | @item 3 (NF_COMPLEX) | |
1248 | @item 4 (NF_COMPLEX16) | |
1249 | @item 5 (NF_COMPLEX32) | |
1250 | These are for complex numbers. A comment in | |
1251 | @file{include/aout/stab_gnu.h} describes them as Fortran complex, double | |
1252 | complex, and complex*16, respectively, but what does that mean? (i.e. | |
1253 | Single precision? Double precison?). | |
1254 | ||
1255 | @item 6 (NF_LDOUBLE) | |
1256 | Long double. It would be cleaner to define a different code for every | |
1257 | possible format of long double. | |
1258 | @end table | |
1259 | ||
1260 | @var{bytes} is the number of bytes occupied by the type. This allows a | |
1261 | debugger to perform some operations with the type even if it doesn't | |
1262 | understand @var{fp_code}. | |
8c59ee11 JK |
1263 | |
1264 | @item g @var{type-information} ; @var{nbits} | |
1265 | Documented by AIX to define a floating type, but their compiler actually | |
1266 | uses negative type numbers (@pxref{Negative Type Numbers}). | |
1267 | ||
1268 | @item c @var{type-information} ; @var{nbits} | |
1269 | Documented by AIX to define a complex type, but their compiler actually | |
1270 | uses negative type numbers (@pxref{Negative Type Numbers}). | |
1271 | @end table | |
1272 | ||
1273 | The C @code{void} type is defined as a signed integral type 0 bits long: | |
1274 | @example | |
1275 | .stabs "void:t19=bs0;0;0",128,0,0,0 | |
1276 | @end example | |
1277 | ||
1278 | I'm not sure how a boolean type is represented. | |
1279 | ||
1280 | @node Negative Type Numbers | |
1281 | @subsection Negative Type numbers | |
1282 | ||
1283 | Since the debugger knows about the builtin types anyway, the idea of | |
1284 | negative type numbers is simply to give a special type number which | |
1285 | indicates the built in type. There is no stab defining these types. | |
1286 | ||
1287 | I'm not sure whether anyone has tried to define what this means if | |
1288 | @code{int} can be other than 32 bits (or other types can be other than | |
1289 | their customary size). If @code{int} has exactly one size for each | |
1290 | architecture, then it can be handled easily enough, but if the size of | |
1291 | @code{int} can vary according the compiler options, then it gets hairy. | |
1292 | I guess the consistent way to do this would be to define separate | |
1293 | negative type numbers for 16-bit @code{int} and 32-bit @code{int}; | |
1294 | therefore I have indicated below the customary size (and other format | |
1295 | information) for each type. The information below is currently correct | |
1296 | because AIX on the RS6000 is the only system which uses these type | |
1297 | numbers. If these type numbers start to get used on other systems, I | |
1298 | suspect the correct thing to do is to define a new number in cases where | |
1299 | a type does not have the size and format indicated below. | |
1300 | ||
1301 | @table @code | |
1302 | @item -1 | |
1303 | @code{int}, 32 bit signed integral type. | |
1304 | ||
1305 | @item -2 | |
1306 | @code{char}, 8 bit type holding a character. Both GDB and dbx on AIX | |
1307 | treat this as signed. GCC uses this type whether @code{char} is signed | |
1308 | or not, which seems like a bad idea. The AIX compiler (xlc) seems to | |
1309 | avoid this type; it uses -5 instead for @code{char}. | |
1310 | ||
1311 | @item -3 | |
1312 | @code{short}, 16 bit signed integral type. | |
1313 | ||
1314 | @item -4 | |
1315 | @code{long}, 32 bit signed integral type. | |
1316 | ||
1317 | @item -5 | |
1318 | @code{unsigned char}, 8 bit unsigned integral type. | |
1319 | ||
1320 | @item -6 | |
1321 | @code{signed char}, 8 bit signed integral type. | |
1322 | ||
1323 | @item -7 | |
1324 | @code{unsigned short}, 16 bit unsigned integral type. | |
1325 | ||
1326 | @item -8 | |
1327 | @code{unsigned int}, 32 bit unsigned integral type. | |
1328 | ||
1329 | @item -9 | |
1330 | @code{unsigned}, 32 bit unsigned integral type. | |
1331 | ||
1332 | @item -10 | |
1333 | @code{unsigned long}, 32 bit unsigned integral type. | |
1334 | ||
1335 | @item -11 | |
1336 | @code{void}, type indicating the lack of a value. | |
1337 | ||
1338 | @item -12 | |
1339 | @code{float}, IEEE single precision. | |
1340 | ||
1341 | @item -13 | |
1342 | @code{double}, IEEE double precision. | |
1343 | ||
1344 | @item -14 | |
1345 | @code{long double}, IEEE extended, RS6000 format. | |
1346 | ||
1347 | @item -15 | |
1348 | @code{integer}. Pascal, I assume. 32 bit signed integral type. | |
1349 | ||
1350 | @item -16 | |
1351 | Boolean. Only one bit is used, not sure about the actual size of the | |
1352 | type. | |
1353 | ||
1354 | @item -17 | |
1355 | @code{short real}. Pascal, I assume. IEEE single precision. | |
1356 | ||
1357 | @item -18 | |
1358 | @code{real}. Pascal, I assume. IEEE double precision. | |
1359 | ||
1360 | @item -19 | |
1361 | A Pascal Stringptr. @xref{Strings}. | |
1362 | ||
1363 | @item -20 | |
1364 | @code{character}, 8 bit unsigned type. | |
1365 | ||
1366 | @item -21 | |
1367 | @code{logical*1}, 8 bit unsigned integral type. | |
1368 | ||
1369 | @item -22 | |
1370 | @code{logical*2}, 16 bit unsigned integral type. | |
1371 | ||
1372 | @item -23 | |
1373 | @code{logical*4}, 32 bit unsigned integral type. | |
1374 | ||
1375 | @item -24 | |
1376 | @code{logical}, 32 bit unsigned integral type. | |
1377 | ||
1378 | @item -25 | |
1379 | A complex type consisting of two IEEE single-precision floating point values. | |
1380 | ||
1381 | @item -26 | |
1382 | A complex type consisting of two IEEE double-precision floating point values. | |
1383 | ||
1384 | @item -27 | |
1385 | @code{integer*1}, 8 bit signed integral type. | |
1386 | ||
1387 | @item -28 | |
1388 | @code{integer*2}, 16 bit signed integral type. | |
1389 | ||
1390 | @item -29 | |
1391 | @code{integer*4}, 32 bit signed integral type. | |
1392 | ||
1393 | @item -30 | |
1394 | Wide character. AIX appears not to use this for the C type | |
1395 | @code{wchar_t}; instead it uses an integral type of the appropriate | |
1396 | size. | |
1397 | @end table | |
1398 | ||
1399 | @node Miscellaneous Types | |
1400 | @section Miscellaneous Types | |
1401 | ||
1402 | @table @code | |
1403 | @item b @var{type-information} ; @var{bytes} | |
1404 | Pascal space type. This is documented by IBM; what does it mean? | |
1405 | ||
1406 | Note that this use of the @samp{b} type descriptor can be distinguished | |
1407 | from its use for builtin integral types (@pxref{Builtin Type | |
1408 | Descriptors}) because the character following the type descriptor is | |
1409 | always a digit, @samp{(}, or @samp{-}. | |
1410 | ||
1411 | @item B @var{type-information} | |
1412 | A volatile-qualified version of @var{type-information}. This is a Sun | |
1413 | extension. A volatile-qualified type means that references and stores | |
1414 | to a variable of that type must not be optimized or cached; they must | |
1415 | occur as the user specifies them. | |
1416 | ||
1417 | @item d @var{type-information} | |
1418 | File of type @var{type-information}. As far as I know this is only used | |
1419 | by Pascal. | |
1420 | ||
1421 | @item k @var{type-information} | |
1422 | A const-qualified version of @var{type-information}. This is a Sun | |
1423 | extension. A const-qualified type means that a variable of this type | |
1424 | cannot be modified. | |
1425 | ||
1426 | @item M @var{type-information} ; @var{length} | |
1427 | Multiple instance type. The type seems to composed of @var{length} | |
1428 | repetitions of @var{type-information}, for example @code{character*3} is | |
1429 | represented by @samp{M-2;3}, where @samp{-2} is a reference to a | |
1430 | character type (@pxref{Negative Type Numbers}). I'm not sure how this | |
1431 | differs from an array. This appears to be a FORTRAN feature. | |
1432 | @var{length} is a bound, like those in range types, @xref{Subranges}. | |
1433 | ||
1434 | @item S @var{type-information} | |
1435 | Pascal set type. @var{type-information} must be a small type such as an | |
1436 | enumeration or a subrange, and the type is a bitmask whose length is | |
1437 | specified by the number of elements in @var{type-information}. | |
1438 | ||
1439 | @item * @var{type-information} | |
1440 | Pointer to @var{type-information}. | |
139741da | 1441 | @end table |
e505224d | 1442 | |
8c59ee11 JK |
1443 | @node Cross-references |
1444 | @section Cross-references to other types | |
1445 | ||
1446 | If a type is used before it is defined, one common way to deal with this | |
1447 | is just to use a type reference to a type which has not yet been | |
1448 | defined. The debugger is expected to be able to deal with this. | |
1449 | ||
1450 | Another way is with the @samp{x} type descriptor, which is followed by | |
1451 | @samp{s} for a structure tag, @samp{u} for a union tag, or @samp{e} for | |
1452 | a enumerator tag, followed by the name of the tag, followed by @samp{:}. | |
1453 | for example the following C declarations: | |
e505224d PB |
1454 | |
1455 | @example | |
8c59ee11 JK |
1456 | struct foo; |
1457 | struct foo *bar; | |
e505224d PB |
1458 | @end example |
1459 | ||
8c59ee11 JK |
1460 | produce |
1461 | ||
1462 | @example | |
1463 | .stabs "bar:G16=*17=xsfoo:",32,0,0,0 | |
1464 | @end example | |
1465 | ||
1466 | Not all debuggers support the @samp{x} type descriptor, so on some | |
1467 | machines GCC does not use it. I believe that for the above example it | |
1468 | would just emit a reference to type 17 and never define it, but I | |
1469 | haven't verified that. | |
1470 | ||
1471 | Modula-2 imported types, at least on AIX, use the @samp{i} type | |
1472 | descriptor, which is followed by the name of the module from which the | |
1473 | type is imported, followed by @samp{:}, followed by the name of the | |
1474 | type. There is then optionally a comma followed by type information for | |
1475 | the type (This differs from merely naming the type (@pxref{Typedefs}) in | |
1476 | that it identifies the module; I don't understand whether the name of | |
1477 | the type given here is always just the same as the name we are giving | |
1478 | it, or whether this type descriptor is used with a nameless stab | |
1479 | (@pxref{Stabs Format}), or what). The symbol ends with @samp{;}. | |
e505224d | 1480 | |
8c59ee11 JK |
1481 | @node Subranges |
1482 | @section Subrange types | |
1483 | ||
1484 | The @samp{r} type descriptor defines a type as a subrange of another | |
1485 | type. It is followed by type information for the type which it is a | |
1486 | subrange of, a semicolon, an integral lower bound, a semicolon, an | |
1487 | integral upper bound, and a semicolon. The AIX documentation does not | |
1488 | specify the trailing semicolon; I believe it is confused. | |
1489 | ||
1490 | AIX allows the bounds to be one of the following instead of an integer: | |
1491 | ||
1492 | @table @code | |
1493 | @item A @var{offset} | |
1494 | The bound is passed by reference on the stack at offset @var{offset} | |
1495 | from the argument list. @xref{Parameters}, for more information on such | |
1496 | offsets. | |
1497 | ||
1498 | @item T @var{offset} | |
1499 | The bound is passed by value on the stack at offset @var{offset} from | |
1500 | the argument list. | |
1501 | ||
1502 | @item a @var{register-number} | |
1503 | The bound is pased by reference in register number | |
1504 | @var{register-number}. | |
1505 | ||
1506 | @item t @var{register-number} | |
1507 | The bound is passed by value in register number @var{register-number}. | |
1508 | ||
1509 | @item J | |
1510 | There is no bound. | |
1511 | @end table | |
1512 | ||
1513 | Subranges are also used for builtin types, @xref{Traditional Builtin Types}. | |
1514 | ||
1515 | @node Arrays | |
1516 | @section Array types | |
1517 | ||
1518 | Arrays use the @samp{a} type descriptor. Following the type descriptor | |
1519 | is the type of the index and the type of the array elements. The two | |
1520 | types types are not separated by any sort of delimiter; if the type of | |
1521 | the index does not end in a semicolon I don't know what is supposed to | |
1522 | happen. IBM documents a semicolon between the two types. For the | |
1523 | common case (a range type), this ends up as being the same since IBM | |
1524 | documents a range type as not ending in a semicolon, but the latter does | |
1525 | not accord with common practice, in which range types do end with | |
1526 | semicolons. | |
6aa83a79 JG |
1527 | |
1528 | The type of the index is often a range type, expressed as the letter r | |
8c59ee11 JK |
1529 | and some parameters. It defines the size of the array. In the example |
1530 | below, the range @code{r1;0;2;} defines an index type which is a | |
1531 | subrange of type 1 (integer), with a lower bound of 0 and an upper bound | |
1532 | of 2. This defines the valid range of subscripts of a three-element C | |
1533 | array. | |
e505224d | 1534 | |
8c59ee11 | 1535 | For example, the definition |
e505224d PB |
1536 | |
1537 | @example | |
8c59ee11 JK |
1538 | char char_vec[3] = @{'a','b','c'@}; |
1539 | @end example | |
e505224d | 1540 | |
8c59ee11 JK |
1541 | @noindent |
1542 | produces the output | |
1543 | ||
1544 | @example | |
1545 | .stabs "char_vec:G19=ar1;0;2;2",32,0,0,0 | |
1546 | .global _char_vec | |
1547 | .align 4 | |
1548 | _char_vec: | |
1549 | .byte 97 | |
1550 | .byte 98 | |
1551 | .byte 99 | |
1552 | @end example | |
1553 | ||
1554 | If an array is @dfn{packed}, it means that the elements are spaced more | |
1555 | closely than normal, saving memory at the expense of speed. For | |
1556 | example, an array of 3-byte objects might, if unpacked, have each | |
1557 | element aligned on a 4-byte boundary, but if packed, have no padding. | |
1558 | One way to specify that something is packed is with type attributes | |
1559 | (@pxref{Stabs Format}), in the case of arrays another is to use the | |
1560 | @samp{P} type descriptor instead of @samp{a}. Other than specifying a | |
1561 | packed array, @samp{P} is identical to @samp{a}. | |
1562 | ||
1563 | @c FIXME-what is it? A pointer? | |
1564 | An open array is represented by the @samp{A} type descriptor followed by | |
1565 | type information specifying the type of the array elements. | |
1566 | ||
1567 | @c FIXME: what is the format of this type? A pointer to a vector of pointers? | |
1568 | An N-dimensional dynamic array is represented by | |
1569 | ||
1570 | @example | |
1571 | D @var{dimensions} ; @var{type-information} | |
1572 | @end example | |
1573 | ||
1574 | @c Does dimensions really have this meaning? The AIX documentation | |
1575 | @c doesn't say. | |
1576 | @var{dimensions} is the number of dimensions; @var{type-information} | |
1577 | specifies the type of the array elements. | |
1578 | ||
1579 | @c FIXME: what is the format of this type? A pointer to some offsets in | |
1580 | @c another array? | |
1581 | A subarray of an N-dimensional array is represented by | |
1582 | ||
1583 | @example | |
1584 | E @var{dimensions} ; @var{type-information} | |
e505224d PB |
1585 | @end example |
1586 | ||
8c59ee11 JK |
1587 | @c Does dimensions really have this meaning? The AIX documentation |
1588 | @c doesn't say. | |
1589 | @var{dimensions} is the number of dimensions; @var{type-information} | |
1590 | specifies the type of the array elements. | |
1591 | ||
1592 | @node Strings | |
1593 | @section Strings | |
1594 | ||
1595 | Some languages, like C or the original Pascal, do not have string types, | |
1596 | they just have related things like arrays of characters. But most | |
1597 | Pascals and various other languages have string types, which are | |
1598 | indicated as follows: | |
1599 | ||
1600 | @table @code | |
1601 | @item n @var{type-information} ; @var{bytes} | |
1602 | @var{bytes} is the maximum length. I'm not sure what | |
1603 | @var{type-information} is; I suspect that it means that this is a string | |
1604 | of @var{type-information} (thus allowing a string of integers, a string | |
1605 | of wide characters, etc., as well as a string of characters). Not sure | |
1606 | what the format of this type is. This is an AIX feature. | |
1607 | ||
1608 | @item z @var{type-information} ; @var{bytes} | |
1609 | Just like @samp{n} except that this is a gstring, not an ordinary | |
1610 | string. I don't know the difference. | |
1611 | ||
1612 | @item N | |
1613 | Pascal Stringptr. What is this? This is an AIX feature. | |
1614 | @end table | |
1615 | ||
899bafeb | 1616 | @node Enumerations |
e505224d PB |
1617 | @section Enumerations |
1618 | ||
8c59ee11 | 1619 | Enumerations are defined with the @samp{e} type descriptor. |
e505224d | 1620 | |
8c59ee11 JK |
1621 | @c FIXME: Where does this information properly go? Perhaps it is |
1622 | @c redundant with something we already explain. | |
e505224d PB |
1623 | The source line below declares an enumeration type. It is defined at |
1624 | file scope between the bodies of main and s_proc in example2.c. | |
8c59ee11 | 1625 | The type definition is located after the N_RBRAC that marks the end of |
e505224d | 1626 | the previous procedure's block scope, and before the N_FUN that marks |
8c59ee11 JK |
1627 | the beginning of the next procedure's block scope. Therefore it does not |
1628 | describe a block local symbol, but a file local one. | |
1629 | ||
1630 | The source line: | |
e505224d PB |
1631 | |
1632 | @example | |
8c59ee11 | 1633 | enum e_places @{first,second=3,last@}; |
e505224d PB |
1634 | @end example |
1635 | ||
899bafeb | 1636 | @noindent |
8c59ee11 | 1637 | generates the following stab |
e505224d | 1638 | |
899bafeb | 1639 | @example |
8c59ee11 | 1640 | .stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0 |
899bafeb | 1641 | @end example |
e505224d PB |
1642 | |
1643 | The symbol descriptor (T) says that the stab describes a structure, | |
1644 | enumeration, or type tag. The type descriptor e, following the 22= of | |
1645 | the type definition narrows it down to an enumeration type. Following | |
1646 | the e is a list of the elements of the enumeration. The format is | |
1647 | name:value,. The list of elements ends with a ;. | |
1648 | ||
8c59ee11 JK |
1649 | There is no standard way to specify the size of an enumeration type; it |
1650 | is determined by the architecture (normally all enumerations types are | |
1651 | 32 bits). There should be a way to specify an enumeration type of | |
1652 | another size; type attributes would be one way to do this @xref{Stabs | |
1653 | Format}. | |
1654 | ||
1655 | @node Structures | |
1656 | @section Structures | |
e505224d | 1657 | |
139741da RP |
1658 | @table @strong |
1659 | @item Directive: | |
1660 | @code{.stabs} | |
1661 | @item Type: | |
8c59ee11 | 1662 | @code{N_LSYM} or @code{C_DECL} |
139741da RP |
1663 | @item Symbol Descriptor: |
1664 | @code{T} | |
1665 | @item Type Descriptor: | |
1666 | @code{s} | |
1667 | @end table | |
e505224d PB |
1668 | |
1669 | The following source code declares a structure tag and defines an | |
4d7f562d | 1670 | instance of the structure in global scope. Then a typedef equates the |
e505224d PB |
1671 | structure tag with a new type. A seperate stab is generated for the |
1672 | structure tag, the structure typedef, and the structure instance. The | |
1673 | stabs for the tag and the typedef are emited when the definitions are | |
1674 | encountered. Since the structure elements are not initialized, the | |
1675 | stab and code for the structure variable itself is located at the end | |
1676 | of the program in .common. | |
1677 | ||
1678 | @example | |
1679 | 6 struct s_tag @{ | |
1680 | 7 int s_int; | |
1681 | 8 float s_float; | |
1682 | 9 char s_char_vec[8]; | |
1683 | 10 struct s_tag* s_next; | |
1684 | 11 @} g_an_s; | |
1685 | 12 | |
1686 | 13 typedef struct s_tag s_typedef; | |
1687 | @end example | |
1688 | ||
1689 | The structure tag is an N_LSYM stab type because, like the enum, the | |
1690 | symbol is file scope. Like the enum, the symbol descriptor is T, for | |
1691 | enumeration, struct or tag type. The symbol descriptor s following | |
1692 | the 16= of the type definition narrows the symbol type to struct. | |
1693 | ||
1694 | Following the struct symbol descriptor is the number of bytes the | |
1695 | struct occupies, followed by a description of each structure element. | |
1696 | The structure element descriptions are of the form name:type, bit | |
1697 | offset from the start of the struct, and number of bits in the | |
1698 | element. | |
1699 | ||
1700 | ||
612dbd4c | 1701 | @example |
e505224d PB |
1702 | <128> N_LSYM - type definition |
1703 | .stabs "name:sym_desc(struct tag) Type_def(16)=type_desc(struct type) | |
139741da | 1704 | struct_bytes |
e505224d | 1705 | elem_name:type_ref(int),bit_offset,field_bits; |
139741da | 1706 | elem_name:type_ref(float),bit_offset,field_bits; |
6aa83a79 JG |
1707 | elem_name:type_def(17)=type_desc(array) |
1708 | index_type(range of int from 0 to 7); | |
1709 | element_type(char),bit_offset,field_bits;;", | |
139741da | 1710 | N_LSYM,NIL,NIL,NIL |
e505224d PB |
1711 | |
1712 | 30 .stabs "s_tag:T16=s20s_int:1,0,32;s_float:12,32,32; | |
139741da | 1713 | s_char_vec:17=ar1;0;7;2,64,64;s_next:18=*16,128,32;;",128,0,0,0 |
612dbd4c | 1714 | @end example |
e505224d PB |
1715 | |
1716 | In this example, two of the structure elements are previously defined | |
1717 | types. For these, the type following the name: part of the element | |
1718 | description is a simple type reference. The other two structure | |
1719 | elements are new types. In this case there is a type definition | |
1720 | embedded after the name:. The type definition for the array element | |
1721 | looks just like a type definition for a standalone array. The s_next | |
1722 | field is a pointer to the same kind of structure that the field is an | |
1723 | element of. So the definition of structure type 16 contains an type | |
1724 | definition for an element which is a pointer to type 16. | |
1725 | ||
899bafeb | 1726 | @node Typedefs |
8c59ee11 | 1727 | @section Giving a type a name |
e505224d | 1728 | |
8c59ee11 | 1729 | To give a type a name, use the @samp{t} symbol descriptor. For example, |
e505224d | 1730 | |
899bafeb | 1731 | @example |
8c59ee11 | 1732 | .stabs "s_typedef:t16",128,0,0,0 |
899bafeb | 1733 | @end example |
e505224d | 1734 | |
8c59ee11 JK |
1735 | specifies that @code{s_typedef} refers to type number 16. Such stabs |
1736 | have symbol type @code{N_LSYM} or @code{C_DECL}. | |
e505224d | 1737 | |
8c59ee11 JK |
1738 | If instead, you are giving a name to a tag for a structure, union, or |
1739 | enumeration, use the @samp{T} symbol descriptor instead. I believe C is | |
1740 | the only language with this feature. | |
e505224d | 1741 | |
8c59ee11 JK |
1742 | If the type is an opaque type (I believe this is a Modula-2 feature), |
1743 | AIX provides a type descriptor to specify it. The type descriptor is | |
1744 | @samp{o} and is followed by a name. I don't know what the name | |
1745 | means---is it always the same as the name of the type, or is this type | |
1746 | descriptor used with a nameless stab (@pxref{Stabs Format})? There | |
1747 | optionally follows a comma followed by type information which defines | |
1748 | the type of this type. If omitted, a semicolon is used in place of the | |
1749 | comma and the type information, and, the type is much like a generic | |
1750 | pointer type---it has a known size but little else about it is | |
1751 | specified. | |
e505224d | 1752 | |
899bafeb | 1753 | @node Unions |
e505224d PB |
1754 | @section Unions |
1755 | ||
612dbd4c | 1756 | Next let's look at unions. In example2 this union type is declared |
e505224d PB |
1757 | locally to a procedure and an instance of the union is defined. |
1758 | ||
1759 | @example | |
1760 | 36 union u_tag @{ | |
1761 | 37 int u_int; | |
1762 | 38 float u_float; | |
1763 | 39 char* u_char; | |
1764 | 40 @} an_u; | |
1765 | @end example | |
1766 | ||
1767 | This code generates a stab for the union tag and a stab for the union | |
1768 | variable. Both use the N_LSYM stab type. Since the union variable is | |
1769 | scoped locally to the procedure in which it is defined, its stab is | |
139741da | 1770 | located immediately preceding the N_LBRAC for the procedure's block |
e505224d PB |
1771 | start. |
1772 | ||
139741da | 1773 | The stab for the union tag, however is located preceding the code for |
e505224d PB |
1774 | the procedure in which it is defined. The stab type is N_LSYM. This |
1775 | would seem to imply that the union type is file scope, like the struct | |
1776 | type s_tag. This is not true. The contents and position of the stab | |
1777 | for u_type do not convey any infomation about its procedure local | |
1778 | scope. | |
1779 | ||
899bafeb | 1780 | @display |
e505224d PB |
1781 | <128> N_LSYM - type |
1782 | .stabs "name:sym_desc(union tag)type_def(22)=type_desc(union) | |
1783 | byte_size(4) | |
1784 | elem_name:type_ref(int),bit_offset(0),bit_size(32); | |
1785 | elem_name:type_ref(float),bit_offset(0),bit_size(32); | |
1786 | elem_name:type_ref(ptr to char),bit_offset(0),bit_size(32);;" | |
1787 | N_LSYM, NIL, NIL, NIL | |
899bafeb | 1788 | @end display |
e505224d | 1789 | |
5bc927fb RP |
1790 | @smallexample |
1791 | 105 .stabs "u_tag:T23=u4u_int:1,0,32;u_float:12,0,32;u_char:21,0,32;;", | |
1792 | 128,0,0,0 | |
1793 | @end smallexample | |
e505224d PB |
1794 | |
1795 | The symbol descriptor, T, following the name: means that the stab | |
4d7f562d | 1796 | describes an enumeration, struct or type tag. The type descriptor u, |
e505224d PB |
1797 | following the 23= of the type definition, narrows it down to a union |
1798 | type definition. Following the u is the number of bytes in the union. | |
1799 | After that is a list of union element descriptions. Their format is | |
1800 | name:type, bit offset into the union, and number of bytes for the | |
1801 | element;. | |
1802 | ||
1803 | The stab for the union variable follows. Notice that the frame | |
1804 | pointer offset for local variables is negative. | |
1805 | ||
899bafeb | 1806 | @display |
e505224d PB |
1807 | <128> N_LSYM - local variable (with no symbol descriptor) |
1808 | .stabs "name:type_ref(u_tag)", N_LSYM, NIL, NIL, frame_ptr_offset | |
899bafeb | 1809 | @end display |
e505224d | 1810 | |
899bafeb | 1811 | @example |
e505224d | 1812 | 130 .stabs "an_u:23",128,0,0,-20 |
899bafeb | 1813 | @end example |
e505224d | 1814 | |
899bafeb | 1815 | @node Function types |
e505224d PB |
1816 | @section Function types |
1817 | ||
8c59ee11 JK |
1818 | There are various types for function variables. These types are not |
1819 | used in defining functions; see symbol descriptor @samp{f}; they are | |
1820 | used for things like pointers to functions. | |
e505224d | 1821 | |
8c59ee11 JK |
1822 | The simple, traditional, type is type descriptor @samp{f} is followed by |
1823 | type information for the return type of the function, followed by a | |
1824 | semicolon. | |
1825 | ||
1826 | This does not deal with functions the number and type of whose | |
1827 | parameters are part of their type, as found in Modula-2 or ANSI C. AIX | |
1828 | provides extensions to specify these, using the @samp{f}, @samp{F}, | |
1829 | @samp{p}, and @samp{R} type descriptors. | |
1830 | ||
1831 | First comes the type descriptor. Then, if it is @samp{f} or @samp{F}, | |
1832 | this is a function, and the type information for the return type of the | |
1833 | function follows, followed by a comma. Then comes the number of | |
1834 | parameters to the function and a semicolon. Then, for each parameter, | |
1835 | there is the name of the parameter followed by a colon (this is only | |
1836 | present for type descriptors @samp{R} and @samp{F} which represent | |
1837 | Pascal function or procedure parameters), type information for the | |
1838 | parameter, a comma, @samp{0} if passed by reference or @samp{1} if | |
1839 | passed by value, and a semicolon. The type definition ends with a | |
1840 | semicolon. | |
1841 | ||
1842 | For example, | |
e505224d PB |
1843 | |
1844 | @example | |
8c59ee11 | 1845 | int (*g_pf)(); |
e505224d PB |
1846 | @end example |
1847 | ||
8c59ee11 JK |
1848 | @noindent |
1849 | generates the following code: | |
e505224d | 1850 | |
899bafeb | 1851 | @example |
8c59ee11 JK |
1852 | .stabs "g_pf:G24=*25=f1",32,0,0,0 |
1853 | .common _g_pf,4,"bss" | |
899bafeb | 1854 | @end example |
e505224d | 1855 | |
8c59ee11 JK |
1856 | The variable defines a new type, 24, which is a pointer to another new |
1857 | type, 25, which is defined as a function returning int. | |
e505224d | 1858 | |
899bafeb | 1859 | @node Symbol tables |
e505224d PB |
1860 | @chapter Symbol information in symbol tables |
1861 | ||
1862 | This section examines more closely the format of symbol table entries | |
1863 | and how stab assembler directives map to them. It also describes what | |
1864 | transformations the assembler and linker make on data from stabs. | |
1865 | ||
1866 | Each time the assembler encounters a stab in its input file it puts | |
1867 | each field of the stab into corresponding fields in a symbol table | |
1868 | entry of its output file. If the stab contains a string field, the | |
1869 | symbol table entry for that stab points to a string table entry | |
1870 | containing the string data from the stab. Assembler labels become | |
1871 | relocatable addresses. Symbol table entries in a.out have the format: | |
1872 | ||
1873 | @example | |
1874 | struct internal_nlist @{ | |
139741da RP |
1875 | unsigned long n_strx; /* index into string table of name */ |
1876 | unsigned char n_type; /* type of symbol */ | |
1877 | unsigned char n_other; /* misc info (usually empty) */ | |
1878 | unsigned short n_desc; /* description field */ | |
1879 | bfd_vma n_value; /* value of symbol */ | |
e505224d PB |
1880 | @}; |
1881 | @end example | |
1882 | ||
1883 | For .stabs directives, the n_strx field holds the character offset | |
1884 | from the start of the string table to the string table entry | |
1885 | containing the "string" field. For other classes of stabs (.stabn and | |
1886 | .stabd) this field is null. | |
1887 | ||
1888 | Symbol table entries with n_type fields containing a value greater or | |
1889 | equal to 0x20 originated as stabs generated by the compiler (with one | |
1890 | random exception). Those with n_type values less than 0x20 were | |
1891 | placed in the symbol table of the executable by the assembler or the | |
1892 | linker. | |
1893 | ||
1894 | The linker concatenates object files and does fixups of externally | |
1895 | defined symbols. You can see the transformations made on stab data by | |
1896 | the assembler and linker by examining the symbol table after each pass | |
1897 | of the build, first the assemble and then the link. | |
1898 | ||
1899 | To do this use nm with the -ap options. This dumps the symbol table, | |
1900 | including debugging information, unsorted. For stab entries the | |
1901 | columns are: value, other, desc, type, string. For assembler and | |
1902 | linker symbols, the columns are: value, type, string. | |
1903 | ||
1904 | There are a few important things to notice about symbol tables. Where | |
1905 | the value field of a stab contains a frame pointer offset, or a | |
1906 | register number, that value is unchanged by the rest of the build. | |
1907 | ||
1908 | Where the value field of a stab contains an assembly language label, | |
1909 | it is transformed by each build step. The assembler turns it into a | |
1910 | relocatable address and the linker turns it into an absolute address. | |
1911 | This source line defines a static variable at file scope: | |
1912 | ||
899bafeb | 1913 | @example |
e505224d | 1914 | 3 static int s_g_repeat |
899bafeb | 1915 | @end example |
e505224d | 1916 | |
899bafeb | 1917 | @noindent |
e505224d PB |
1918 | The following stab describes the symbol. |
1919 | ||
899bafeb | 1920 | @example |
e505224d | 1921 | 26 .stabs "s_g_repeat:S1",38,0,0,_s_g_repeat |
899bafeb | 1922 | @end example |
e505224d | 1923 | |
899bafeb | 1924 | @noindent |
e505224d | 1925 | The assembler transforms the stab into this symbol table entry in the |
899bafeb | 1926 | @file{.o} file. The location is expressed as a data segment offset. |
e505224d | 1927 | |
899bafeb | 1928 | @example |
e505224d | 1929 | 21 00000084 - 00 0000 STSYM s_g_repeat:S1 |
899bafeb | 1930 | @end example |
e505224d | 1931 | |
899bafeb | 1932 | @noindent |
e505224d PB |
1933 | in the symbol table entry from the executable, the linker has made the |
1934 | relocatable address absolute. | |
1935 | ||
899bafeb | 1936 | @example |
e505224d | 1937 | 22 0000e00c - 00 0000 STSYM s_g_repeat:S1 |
899bafeb | 1938 | @end example |
e505224d PB |
1939 | |
1940 | Stabs for global variables do not contain location information. In | |
1941 | this case the debugger finds location information in the assembler or | |
1942 | linker symbol table entry describing the variable. The source line: | |
1943 | ||
899bafeb | 1944 | @example |
e505224d | 1945 | 1 char g_foo = 'c'; |
899bafeb | 1946 | @end example |
e505224d | 1947 | |
899bafeb | 1948 | @noindent |
e505224d PB |
1949 | generates the stab: |
1950 | ||
899bafeb | 1951 | @example |
e505224d | 1952 | 21 .stabs "g_foo:G2",32,0,0,0 |
899bafeb | 1953 | @end example |
e505224d PB |
1954 | |
1955 | The variable is represented by the following two symbol table entries | |
1956 | in the object file. The first one originated as a stab. The second | |
1957 | one is an external symbol. The upper case D signifies that the n_type | |
1958 | field of the symbol table contains 7, N_DATA with local linkage (see | |
1959 | Table B). The value field following the file's line number is empty | |
1960 | for the stab entry. For the linker symbol it contains the | |
1961 | rellocatable address corresponding to the variable. | |
1962 | ||
899bafeb | 1963 | @example |
e505224d PB |
1964 | 19 00000000 - 00 0000 GSYM g_foo:G2 |
1965 | 20 00000080 D _g_foo | |
899bafeb | 1966 | @end example |
e505224d | 1967 | |
899bafeb | 1968 | @noindent |
e505224d PB |
1969 | These entries as transformed by the linker. The linker symbol table |
1970 | entry now holds an absolute address. | |
1971 | ||
899bafeb | 1972 | @example |
e505224d | 1973 | 21 00000000 - 00 0000 GSYM g_foo:G2 |
899bafeb | 1974 | @dots{} |
e505224d | 1975 | 215 0000e008 D _g_foo |
899bafeb | 1976 | @end example |
e505224d | 1977 | |
8c59ee11 | 1978 | @node Cplusplus |
612dbd4c | 1979 | @chapter GNU C++ stabs |
e505224d PB |
1980 | |
1981 | @menu | |
b32ae57b | 1982 | * Basic Cplusplus types:: |
e505224d PB |
1983 | * Simple classes:: |
1984 | * Class instance:: | |
1985 | * Methods:: Method definition | |
1986 | * Protections:: | |
2dd00294 JG |
1987 | * Method Modifiers:: (const, volatile, const volatile) |
1988 | * Virtual Methods:: | |
1989 | * Inheritence:: | |
1990 | * Virtual Base Classes:: | |
1991 | * Static Members:: | |
e505224d PB |
1992 | @end menu |
1993 | ||
e505224d PB |
1994 | @subsection type descriptors added for C++ descriptions |
1995 | ||
1996 | @table @code | |
1997 | @item # | |
1998 | method type (two ## if minimal debug) | |
1999 | ||
8c59ee11 JK |
2000 | @item @@ |
2001 | Member (class and variable) type. It is followed by type information | |
2002 | for the offset basetype, a comma, and type information for the type of | |
2003 | the field being pointed to. (FIXME: this is acknowledged to be | |
2004 | gibberish. Can anyone say what really goes here?). | |
2005 | ||
2006 | Note that there is a conflict between this and type attributes | |
2007 | (@pxref{Stabs Format}); both use type descriptor @samp{@@}. | |
2008 | Fortunately, the @samp{@@} type descriptor used in this C++ sense always | |
2009 | will be followed by a digit, @samp{(}, or @samp{-}, and type attributes | |
2010 | never start with those things. | |
e505224d PB |
2011 | @end table |
2012 | ||
b32ae57b | 2013 | @node Basic Cplusplus types |
e505224d PB |
2014 | @section Basic types for C++ |
2015 | ||
2016 | << the examples that follow are based on a01.C >> | |
2017 | ||
2018 | ||
2019 | C++ adds two more builtin types to the set defined for C. These are | |
2020 | the unknown type and the vtable record type. The unknown type, type | |
2021 | 16, is defined in terms of itself like the void type. | |
2022 | ||
2023 | The vtable record type, type 17, is defined as a structure type and | |
2024 | then as a structure tag. The structure has four fields, delta, index, | |
2025 | pfn, and delta2. pfn is the function pointer. | |
2026 | ||
2027 | << In boilerplate $vtbl_ptr_type, what are the fields delta, | |
2028 | index, and delta2 used for? >> | |
2029 | ||
2030 | This basic type is present in all C++ programs even if there are no | |
2031 | virtual methods defined. | |
2032 | ||
899bafeb | 2033 | @display |
e505224d | 2034 | .stabs "struct_name:sym_desc(type)type_def(17)=type_desc(struct)struct_bytes(8) |
139741da RP |
2035 | elem_name(delta):type_ref(short int),bit_offset(0),field_bits(16); |
2036 | elem_name(index):type_ref(short int),bit_offset(16),field_bits(16); | |
2037 | elem_name(pfn):type_def(18)=type_desc(ptr to)type_ref(void), | |
2038 | bit_offset(32),field_bits(32); | |
2039 | elem_name(delta2):type_def(short int);bit_offset(32),field_bits(16);;" | |
2040 | N_LSYM, NIL, NIL | |
899bafeb | 2041 | @end display |
139741da | 2042 | |
899bafeb | 2043 | @smallexample |
e505224d | 2044 | .stabs "$vtbl_ptr_type:t17=s8 |
139741da RP |
2045 | delta:6,0,16;index:6,16,16;pfn:18=*15,32,32;delta2:6,32,16;;" |
2046 | ,128,0,0,0 | |
899bafeb | 2047 | @end smallexample |
e505224d | 2048 | |
899bafeb | 2049 | @display |
e505224d | 2050 | .stabs "name:sym_dec(struct tag)type_ref($vtbl_ptr_type)",N_LSYM,NIL,NIL,NIL |
899bafeb | 2051 | @end display |
e505224d | 2052 | |
899bafeb | 2053 | @example |
e505224d | 2054 | .stabs "$vtbl_ptr_type:T17",128,0,0,0 |
899bafeb | 2055 | @end example |
e505224d | 2056 | |
899bafeb | 2057 | @node Simple classes |
e505224d PB |
2058 | @section Simple class definition |
2059 | ||
2060 | The stabs describing C++ language features are an extension of the | |
2061 | stabs describing C. Stabs representing C++ class types elaborate | |
2062 | extensively on the stab format used to describe structure types in C. | |
2063 | Stabs representing class type variables look just like stabs | |
2064 | representing C language variables. | |
2065 | ||
2066 | Consider the following very simple class definition. | |
2067 | ||
2068 | @example | |
2069 | class baseA @{ | |
2070 | public: | |
139741da RP |
2071 | int Adat; |
2072 | int Ameth(int in, char other); | |
e505224d PB |
2073 | @}; |
2074 | @end example | |
2075 | ||
2076 | The class baseA is represented by two stabs. The first stab describes | |
2077 | the class as a structure type. The second stab describes a structure | |
2078 | tag of the class type. Both stabs are of stab type N_LSYM. Since the | |
2079 | stab is not located between an N_FUN and a N_LBRAC stab this indicates | |
2080 | that the class is defined at file scope. If it were, then the N_LSYM | |
2081 | would signify a local variable. | |
2082 | ||
2083 | A stab describing a C++ class type is similar in format to a stab | |
2084 | describing a C struct, with each class member shown as a field in the | |
2085 | structure. The part of the struct format describing fields is | |
2086 | expanded to include extra information relevent to C++ class members. | |
2087 | In addition, if the class has multiple base classes or virtual | |
2088 | functions the struct format outside of the field parts is also | |
2089 | augmented. | |
2090 | ||
2091 | In this simple example the field part of the C++ class stab | |
2092 | representing member data looks just like the field part of a C struct | |
2093 | stab. The section on protections describes how its format is | |
2094 | sometimes extended for member data. | |
2095 | ||
2096 | The field part of a C++ class stab representing a member function | |
2097 | differs substantially from the field part of a C struct stab. It | |
2098 | still begins with `name:' but then goes on to define a new type number | |
2099 | for the member function, describe its return type, its argument types, | |
2100 | its protection level, any qualifiers applied to the method definition, | |
2101 | and whether the method is virtual or not. If the method is virtual | |
2102 | then the method description goes on to give the vtable index of the | |
2103 | method, and the type number of the first base class defining the | |
2104 | method. | |
2105 | ||
2106 | When the field name is a method name it is followed by two colons | |
2107 | rather than one. This is followed by a new type definition for the | |
2108 | method. This is a number followed by an equal sign and then the | |
2109 | symbol descriptor `##', indicating a method type. This is followed by | |
2110 | a type reference showing the return type of the method and a | |
2111 | semi-colon. | |
2112 | ||
2113 | The format of an overloaded operator method name differs from that | |
2114 | of other methods. It is "op$::XXXX." where XXXX is the operator name | |
612dbd4c JG |
2115 | such as + or +=. The name ends with a period, and any characters except |
2116 | the period can occur in the XXXX string. | |
e505224d PB |
2117 | |
2118 | The next part of the method description represents the arguments to | |
2119 | the method, preceeded by a colon and ending with a semi-colon. The | |
2120 | types of the arguments are expressed in the same way argument types | |
2121 | are expressed in C++ name mangling. In this example an int and a char | |
2122 | map to `ic'. | |
2123 | ||
2124 | This is followed by a number, a letter, and an asterisk or period, | |
2125 | followed by another semicolon. The number indicates the protections | |
2126 | that apply to the member function. Here the 2 means public. The | |
2127 | letter encodes any qualifier applied to the method definition. In | |
2128 | this case A means that it is a normal function definition. The dot | |
2129 | shows that the method is not virtual. The sections that follow | |
2130 | elaborate further on these fields and describe the additional | |
2131 | information present for virtual methods. | |
2132 | ||
2133 | ||
899bafeb | 2134 | @display |
e505224d | 2135 | .stabs "class_name:sym_desc(type)type_def(20)=type_desc(struct)struct_bytes(4) |
139741da | 2136 | field_name(Adat):type(int),bit_offset(0),field_bits(32); |
e505224d | 2137 | |
139741da RP |
2138 | method_name(Ameth)::type_def(21)=type_desc(method)return_type(int); |
2139 | :arg_types(int char); | |
2140 | protection(public)qualifier(normal)virtual(no);;" | |
2141 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2142 | @end display |
e505224d | 2143 | |
899bafeb | 2144 | @smallexample |
e505224d PB |
2145 | .stabs "baseA:t20=s4Adat:1,0,32;Ameth::21=##1;:ic;2A.;;",128,0,0,0 |
2146 | ||
2147 | .stabs "class_name:sym_desc(struct tag)",N_LSYM,NIL,NIL,NIL | |
2148 | ||
2149 | .stabs "baseA:T20",128,0,0,0 | |
899bafeb | 2150 | @end smallexample |
e505224d | 2151 | |
899bafeb | 2152 | @node Class instance |
e505224d PB |
2153 | @section Class instance |
2154 | ||
2155 | As shown above, describing even a simple C++ class definition is | |
2156 | accomplished by massively extending the stab format used in C to | |
2157 | describe structure types. However, once the class is defined, C stabs | |
2158 | with no modifications can be used to describe class instances. The | |
2159 | following source: | |
2160 | ||
2161 | @example | |
2162 | main () @{ | |
139741da | 2163 | baseA AbaseA; |
e505224d PB |
2164 | @} |
2165 | @end example | |
2166 | ||
899bafeb RP |
2167 | @noindent |
2168 | yields the following stab describing the class instance. It looks no | |
e505224d PB |
2169 | different from a standard C stab describing a local variable. |
2170 | ||
899bafeb | 2171 | @display |
e505224d | 2172 | .stabs "name:type_ref(baseA)", N_LSYM, NIL, NIL, frame_ptr_offset |
899bafeb | 2173 | @end display |
e505224d | 2174 | |
899bafeb | 2175 | @example |
e505224d | 2176 | .stabs "AbaseA:20",128,0,0,-20 |
899bafeb | 2177 | @end example |
e505224d | 2178 | |
899bafeb | 2179 | @node Methods |
e505224d PB |
2180 | @section Method defintion |
2181 | ||
2182 | The class definition shown above declares Ameth. The C++ source below | |
2183 | defines Ameth: | |
2184 | ||
2185 | @example | |
2186 | int | |
2187 | baseA::Ameth(int in, char other) | |
2188 | @{ | |
139741da | 2189 | return in; |
e505224d PB |
2190 | @}; |
2191 | @end example | |
2192 | ||
2193 | ||
2194 | This method definition yields three stabs following the code of the | |
2195 | method. One stab describes the method itself and following two | |
2196 | describe its parameters. Although there is only one formal argument | |
2197 | all methods have an implicit argument which is the `this' pointer. | |
2198 | The `this' pointer is a pointer to the object on which the method was | |
2199 | called. Note that the method name is mangled to encode the class name | |
2200 | and argument types. << Name mangling is not described by this | |
2201 | document - Is there already such a doc? >> | |
2202 | ||
612dbd4c | 2203 | @example |
e505224d | 2204 | .stabs "name:symbol_desriptor(global function)return_type(int)", |
139741da | 2205 | N_FUN, NIL, NIL, code_addr_of_method_start |
e505224d PB |
2206 | |
2207 | .stabs "Ameth__5baseAic:F1",36,0,0,_Ameth__5baseAic | |
612dbd4c | 2208 | @end example |
e505224d PB |
2209 | |
2210 | Here is the stab for the `this' pointer implicit argument. The name | |
c2dc518b | 2211 | of the `this' pointer is always `this.' Type 19, the `this' pointer is |
e505224d PB |
2212 | defined as a pointer to type 20, baseA, but a stab defining baseA has |
2213 | not yet been emited. Since the compiler knows it will be emited | |
2214 | shortly, here it just outputs a cross reference to the undefined | |
2215 | symbol, by prefixing the symbol name with xs. | |
2216 | ||
612dbd4c | 2217 | @example |
e505224d | 2218 | .stabs "name:sym_desc(register param)type_def(19)= |
139741da | 2219 | type_desc(ptr to)type_ref(baseA)= |
e505224d PB |
2220 | type_desc(cross-reference to)baseA:",N_RSYM,NIL,NIL,register_number |
2221 | ||
c2dc518b | 2222 | .stabs "this:P19=*20=xsbaseA:",64,0,0,8 |
612dbd4c | 2223 | @end example |
e505224d PB |
2224 | |
2225 | The stab for the explicit integer argument looks just like a parameter | |
2226 | to a C function. The last field of the stab is the offset from the | |
2227 | argument pointer, which in most systems is the same as the frame | |
2228 | pointer. | |
2229 | ||
612dbd4c | 2230 | @example |
e505224d | 2231 | .stabs "name:sym_desc(value parameter)type_ref(int)", |
139741da | 2232 | N_PSYM,NIL,NIL,offset_from_arg_ptr |
e505224d PB |
2233 | |
2234 | .stabs "in:p1",160,0,0,72 | |
612dbd4c | 2235 | @end example |
e505224d PB |
2236 | |
2237 | << The examples that follow are based on A1.C >> | |
2238 | ||
899bafeb | 2239 | @node Protections |
e505224d PB |
2240 | @section Protections |
2241 | ||
2242 | ||
2243 | In the simple class definition shown above all member data and | |
2244 | functions were publicly accessable. The example that follows | |
2245 | contrasts public, protected and privately accessable fields and shows | |
2246 | how these protections are encoded in C++ stabs. | |
2247 | ||
2248 | Protections for class member data are signified by two characters | |
2249 | embeded in the stab defining the class type. These characters are | |
2250 | located after the name: part of the string. /0 means private, /1 | |
2251 | means protected, and /2 means public. If these characters are omited | |
2252 | this means that the member is public. The following C++ source: | |
2253 | ||
2254 | @example | |
2255 | class all_data @{ | |
139741da RP |
2256 | private: |
2257 | int priv_dat; | |
e505224d | 2258 | protected: |
139741da | 2259 | char prot_dat; |
e505224d | 2260 | public: |
139741da | 2261 | float pub_dat; |
e505224d PB |
2262 | @}; |
2263 | @end example | |
2264 | ||
899bafeb | 2265 | @noindent |
e505224d PB |
2266 | generates the following stab to describe the class type all_data. |
2267 | ||
899bafeb | 2268 | @display |
e505224d | 2269 | .stabs "class_name:sym_desc(type)type_def(19)=type_desc(struct)struct_bytes |
139741da RP |
2270 | data_name:/protection(private)type_ref(int),bit_offset,num_bits; |
2271 | data_name:/protection(protected)type_ref(char),bit_offset,num_bits; | |
2272 | data_name:(/num omited, private)type_ref(float),bit_offset,num_bits;;" | |
2273 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2274 | @end display |
e505224d | 2275 | |
899bafeb | 2276 | @smallexample |
e505224d | 2277 | .stabs "all_data:t19=s12 |
139741da | 2278 | priv_dat:/01,0,32;prot_dat:/12,32,8;pub_dat:12,64,32;;",128,0,0,0 |
899bafeb | 2279 | @end smallexample |
e505224d PB |
2280 | |
2281 | Protections for member functions are signified by one digit embeded in | |
2282 | the field part of the stab describing the method. The digit is 0 if | |
2283 | private, 1 if protected and 2 if public. Consider the C++ class | |
2284 | definition below: | |
2285 | ||
2286 | @example | |
2287 | class all_methods @{ | |
2288 | private: | |
139741da | 2289 | int priv_meth(int in)@{return in;@}; |
e505224d | 2290 | protected: |
139741da | 2291 | char protMeth(char in)@{return in;@}; |
e505224d | 2292 | public: |
139741da | 2293 | float pubMeth(float in)@{return in;@}; |
e505224d PB |
2294 | @}; |
2295 | @end example | |
2296 | ||
2297 | It generates the following stab. The digit in question is to the left | |
2298 | of an `A' in each case. Notice also that in this case two symbol | |
2299 | descriptors apply to the class name struct tag and struct type. | |
2300 | ||
899bafeb | 2301 | @display |
e505224d | 2302 | .stabs "class_name:sym_desc(struct tag&type)type_def(21)= |
139741da RP |
2303 | sym_desc(struct)struct_bytes(1) |
2304 | meth_name::type_def(22)=sym_desc(method)returning(int); | |
2305 | :args(int);protection(private)modifier(normal)virtual(no); | |
2306 | meth_name::type_def(23)=sym_desc(method)returning(char); | |
2307 | :args(char);protection(protected)modifier(normal)virual(no); | |
2308 | meth_name::type_def(24)=sym_desc(method)returning(float); | |
2309 | :args(float);protection(public)modifier(normal)virtual(no);;", | |
2310 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2311 | @end display |
139741da | 2312 | |
899bafeb | 2313 | @smallexample |
e505224d | 2314 | .stabs "all_methods:Tt21=s1priv_meth::22=##1;:i;0A.;protMeth::23=##2;:c;1A.; |
139741da | 2315 | pubMeth::24=##12;:f;2A.;;",128,0,0,0 |
899bafeb | 2316 | @end smallexample |
e505224d | 2317 | |
899bafeb RP |
2318 | @node Method Modifiers |
2319 | @section Method Modifiers (const, volatile, const volatile) | |
e505224d PB |
2320 | |
2321 | << based on a6.C >> | |
2322 | ||
2323 | In the class example described above all the methods have the normal | |
2324 | modifier. This method modifier information is located just after the | |
2325 | protection information for the method. This field has four possible | |
2326 | character values. Normal methods use A, const methods use B, volatile | |
2327 | methods use C, and const volatile methods use D. Consider the class | |
2328 | definition below: | |
2329 | ||
2330 | @example | |
2331 | class A @{ | |
2332 | public: | |
139741da RP |
2333 | int ConstMeth (int arg) const @{ return arg; @}; |
2334 | char VolatileMeth (char arg) volatile @{ return arg; @}; | |
2335 | float ConstVolMeth (float arg) const volatile @{return arg; @}; | |
e505224d PB |
2336 | @}; |
2337 | @end example | |
2338 | ||
2339 | This class is described by the following stab: | |
2340 | ||
899bafeb | 2341 | @display |
e505224d | 2342 | .stabs "class(A):sym_desc(struct)type_def(20)=type_desc(struct)struct_bytes(1) |
139741da RP |
2343 | meth_name(ConstMeth)::type_def(21)sym_desc(method) |
2344 | returning(int);:arg(int);protection(public)modifier(const)virtual(no); | |
2345 | meth_name(VolatileMeth)::type_def(22)=sym_desc(method) | |
2346 | returning(char);:arg(char);protection(public)modifier(volatile)virt(no) | |
2347 | meth_name(ConstVolMeth)::type_def(23)=sym_desc(method) | |
2348 | returning(float);:arg(float);protection(public)modifer(const volatile) | |
2349 | virtual(no);;", @dots{} | |
899bafeb | 2350 | @end display |
139741da | 2351 | |
899bafeb | 2352 | @example |
e505224d | 2353 | .stabs "A:T20=s1ConstMeth::21=##1;:i;2B.;VolatileMeth::22=##2;:c;2C.; |
139741da | 2354 | ConstVolMeth::23=##12;:f;2D.;;",128,0,0,0 |
612dbd4c | 2355 | @end example |
e505224d | 2356 | |
899bafeb | 2357 | @node Virtual Methods |
e505224d PB |
2358 | @section Virtual Methods |
2359 | ||
2360 | << The following examples are based on a4.C >> | |
2361 | ||
2362 | The presence of virtual methods in a class definition adds additional | |
2363 | data to the class description. The extra data is appended to the | |
2364 | description of the virtual method and to the end of the class | |
2365 | description. Consider the class definition below: | |
2366 | ||
2367 | @example | |
2368 | class A @{ | |
2369 | public: | |
139741da RP |
2370 | int Adat; |
2371 | virtual int A_virt (int arg) @{ return arg; @}; | |
e505224d PB |
2372 | @}; |
2373 | @end example | |
2374 | ||
2375 | This results in the stab below describing class A. It defines a new | |
2376 | type (20) which is an 8 byte structure. The first field of the class | |
2377 | struct is Adat, an integer, starting at structure offset 0 and | |
2378 | occupying 32 bits. | |
2379 | ||
2380 | The second field in the class struct is not explicitly defined by the | |
2381 | C++ class definition but is implied by the fact that the class | |
2382 | contains a virtual method. This field is the vtable pointer. The | |
2383 | name of the vtable pointer field starts with $vf and continues with a | |
2384 | type reference to the class it is part of. In this example the type | |
2385 | reference for class A is 20 so the name of its vtable pointer field is | |
2386 | $vf20, followed by the usual colon. | |
2387 | ||
2388 | Next there is a type definition for the vtable pointer type (21). | |
2389 | This is in turn defined as a pointer to another new type (22). | |
2390 | ||
2391 | Type 22 is the vtable itself, which is defined as an array, indexed by | |
6aa83a79 JG |
2392 | a range of integers between 0 and 1, and whose elements are of type |
2393 | 17. Type 17 was the vtable record type defined by the boilerplate C++ | |
2394 | type definitions, as shown earlier. | |
e505224d PB |
2395 | |
2396 | The bit offset of the vtable pointer field is 32. The number of bits | |
2397 | in the field are not specified when the field is a vtable pointer. | |
2398 | ||
2399 | Next is the method definition for the virtual member function A_virt. | |
2400 | Its description starts out using the same format as the non-virtual | |
2401 | member functions described above, except instead of a dot after the | |
2402 | `A' there is an asterisk, indicating that the function is virtual. | |
2403 | Since is is virtual some addition information is appended to the end | |
2404 | of the method description. | |
2405 | ||
2406 | The first number represents the vtable index of the method. This is a | |
2407 | 32 bit unsigned number with the high bit set, followed by a | |
2408 | semi-colon. | |
2409 | ||
2410 | The second number is a type reference to the first base class in the | |
2411 | inheritence hierarchy defining the virtual member function. In this | |
2412 | case the class stab describes a base class so the virtual function is | |
2413 | not overriding any other definition of the method. Therefore the | |
2414 | reference is to the type number of the class that the stab is | |
2415 | describing (20). | |
2416 | ||
2417 | This is followed by three semi-colons. One marks the end of the | |
2418 | current sub-section, one marks the end of the method field, and the | |
2419 | third marks the end of the struct definition. | |
2420 | ||
2421 | For classes containing virtual functions the very last section of the | |
2422 | string part of the stab holds a type reference to the first base | |
2423 | class. This is preceeded by `~%' and followed by a final semi-colon. | |
2424 | ||
899bafeb | 2425 | @display |
e505224d | 2426 | .stabs "class_name(A):type_def(20)=sym_desc(struct)struct_bytes(8) |
139741da RP |
2427 | field_name(Adat):type_ref(int),bit_offset(0),field_bits(32); |
2428 | field_name(A virt func ptr):type_def(21)=type_desc(ptr to)type_def(22)= | |
6aa83a79 JG |
2429 | sym_desc(array)index_type_ref(range of int from 0 to 1); |
2430 | elem_type_ref(vtbl elem type), | |
139741da RP |
2431 | bit_offset(32); |
2432 | meth_name(A_virt)::typedef(23)=sym_desc(method)returning(int); | |
2433 | :arg_type(int),protection(public)normal(yes)virtual(yes) | |
2434 | vtable_index(1);class_first_defining(A);;;~%first_base(A);", | |
2435 | N_LSYM,NIL,NIL,NIL | |
899bafeb | 2436 | @end display |
e505224d | 2437 | |
899bafeb | 2438 | @example |
e505224d | 2439 | .stabs "A:t20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32;A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0 |
612dbd4c | 2440 | @end example |
e505224d | 2441 | |
2dd00294 JG |
2442 | @node Inheritence |
2443 | @section Inheritence | |
e505224d PB |
2444 | |
2445 | Stabs describing C++ derived classes include additional sections that | |
2446 | describe the inheritence hierarchy of the class. A derived class stab | |
2447 | also encodes the number of base classes. For each base class it tells | |
2448 | if the base class is virtual or not, and if the inheritence is private | |
2449 | or public. It also gives the offset into the object of the portion of | |
2450 | the object corresponding to each base class. | |
2451 | ||
2452 | This additional information is embeded in the class stab following the | |
2453 | number of bytes in the struct. First the number of base classes | |
2454 | appears bracketed by an exclamation point and a comma. | |
2455 | ||
2456 | Then for each base type there repeats a series: two digits, a number, | |
2457 | a comma, another number, and a semi-colon. | |
2458 | ||
2459 | The first of the two digits is 1 if the base class is virtual and 0 if | |
2460 | not. The second digit is 2 if the derivation is public and 0 if not. | |
2461 | ||
2462 | The number following the first two digits is the offset from the start | |
2463 | of the object to the part of the object pertaining to the base class. | |
2464 | ||
2465 | After the comma, the second number is a type_descriptor for the base | |
2466 | type. Finally a semi-colon ends the series, which repeats for each | |
2467 | base class. | |
2468 | ||
2469 | The source below defines three base classes A, B, and C and the | |
2470 | derived class D. | |
2471 | ||
2472 | ||
2473 | @example | |
2474 | class A @{ | |
2475 | public: | |
139741da RP |
2476 | int Adat; |
2477 | virtual int A_virt (int arg) @{ return arg; @}; | |
e505224d PB |
2478 | @}; |
2479 | ||
2480 | class B @{ | |
2481 | public: | |
139741da RP |
2482 | int B_dat; |
2483 | virtual int B_virt (int arg) @{return arg; @}; | |
e505224d PB |
2484 | @}; |
2485 | ||
2486 | class C @{ | |
2487 | public: | |
139741da RP |
2488 | int Cdat; |
2489 | virtual int C_virt (int arg) @{return arg; @}; | |
e505224d PB |
2490 | @}; |
2491 | ||
2492 | class D : A, virtual B, public C @{ | |
2493 | public: | |
139741da RP |
2494 | int Ddat; |
2495 | virtual int A_virt (int arg ) @{ return arg+1; @}; | |
2496 | virtual int B_virt (int arg) @{ return arg+2; @}; | |
2497 | virtual int C_virt (int arg) @{ return arg+3; @}; | |
2498 | virtual int D_virt (int arg) @{ return arg; @}; | |
e505224d PB |
2499 | @}; |
2500 | @end example | |
2501 | ||
2502 | Class stabs similar to the ones described earlier are generated for | |
2503 | each base class. | |
2504 | ||
5bc927fb RP |
2505 | @c FIXME!!! the linebreaks in the following example probably make the |
2506 | @c examples literally unusable, but I don't know any other way to get | |
2507 | @c them on the page. | |
899bafeb | 2508 | @smallexample |
5bc927fb RP |
2509 | .stabs "A:T20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32; |
2510 | A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0 | |
e505224d | 2511 | |
5bc927fb RP |
2512 | .stabs "B:Tt25=s8Bdat:1,0,32;$vf25:21,32;B_virt::26=##1; |
2513 | :i;2A*-2147483647;25;;;~%25;",128,0,0,0 | |
e505224d | 2514 | |
5bc927fb RP |
2515 | .stabs "C:Tt28=s8Cdat:1,0,32;$vf28:21,32;C_virt::29=##1; |
2516 | :i;2A*-2147483647;28;;;~%28;",128,0,0,0 | |
899bafeb | 2517 | @end smallexample |
e505224d PB |
2518 | |
2519 | In the stab describing derived class D below, the information about | |
2520 | the derivation of this class is encoded as follows. | |
2521 | ||
899bafeb | 2522 | @display |
e505224d | 2523 | .stabs "derived_class_name:symbol_descriptors(struct tag&type)= |
139741da RP |
2524 | type_descriptor(struct)struct_bytes(32)!num_bases(3), |
2525 | base_virtual(no)inheritence_public(no)base_offset(0), | |
2526 | base_class_type_ref(A); | |
2527 | base_virtual(yes)inheritence_public(no)base_offset(NIL), | |
2528 | base_class_type_ref(B); | |
2529 | base_virtual(no)inheritence_public(yes)base_offset(64), | |
2530 | base_class_type_ref(C); @dots{} | |
899bafeb | 2531 | @end display |
139741da | 2532 | |
5bc927fb | 2533 | @c FIXME! fake linebreaks. |
899bafeb | 2534 | @smallexample |
5bc927fb RP |
2535 | .stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat: |
2536 | 1,160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt: | |
2537 | :32:i;2A*-2147483647;25;;C_virt::32:i;2A*-2147483647; | |
2538 | 28;;D_virt::32:i;2A*-2147483646;31;;;~%20;",128,0,0,0 | |
899bafeb | 2539 | @end smallexample |
e505224d | 2540 | |
2dd00294 | 2541 | @node Virtual Base Classes |
e505224d PB |
2542 | @section Virtual Base Classes |
2543 | ||
2544 | A derived class object consists of a concatination in memory of the | |
2545 | data areas defined by each base class, starting with the leftmost and | |
2546 | ending with the rightmost in the list of base classes. The exception | |
2547 | to this rule is for virtual inheritence. In the example above, class | |
2548 | D inherits virtually from base class B. This means that an instance | |
2549 | of a D object will not contain it's own B part but merely a pointer to | |
2550 | a B part, known as a virtual base pointer. | |
2551 | ||
2552 | In a derived class stab, the base offset part of the derivation | |
2553 | information, described above, shows how the base class parts are | |
2554 | ordered. The base offset for a virtual base class is always given as | |
2555 | 0. Notice that the base offset for B is given as 0 even though B is | |
2556 | not the first base class. The first base class A starts at offset 0. | |
2557 | ||
2558 | The field information part of the stab for class D describes the field | |
2559 | which is the pointer to the virtual base class B. The vbase pointer | |
2560 | name is $vb followed by a type reference to the virtual base class. | |
2561 | Since the type id for B in this example is 25, the vbase pointer name | |
2562 | is $vb25. | |
2563 | ||
5bc927fb | 2564 | @c FIXME!! fake linebreaks below |
899bafeb | 2565 | @smallexample |
5bc927fb RP |
2566 | .stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat:1, |
2567 | 160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt::32:i; | |
2568 | 2A*-2147483647;25;;C_virt::32:i;2A*-2147483647;28;;D_virt: | |
2569 | :32:i;2A*-2147483646;31;;;~%20;",128,0,0,0 | |
899bafeb | 2570 | @end smallexample |
e505224d PB |
2571 | |
2572 | Following the name and a semicolon is a type reference describing the | |
2573 | type of the virtual base class pointer, in this case 24. Type 24 was | |
c2dc518b | 2574 | defined earlier as the type of the B class `this` pointer. The |
e505224d PB |
2575 | `this' pointer for a class is a pointer to the class type. |
2576 | ||
899bafeb | 2577 | @example |
c2dc518b | 2578 | .stabs "this:P24=*25=xsB:",64,0,0,8 |
899bafeb | 2579 | @end example |
e505224d PB |
2580 | |
2581 | Finally the field offset part of the vbase pointer field description | |
2582 | shows that the vbase pointer is the first field in the D object, | |
2583 | before any data fields defined by the class. The layout of a D class | |
2584 | object is a follows, Adat at 0, the vtable pointer for A at 32, Cdat | |
2585 | at 64, the vtable pointer for C at 96, the virtual ase pointer for B | |
2586 | at 128, and Ddat at 160. | |
2587 | ||
2588 | ||
899bafeb | 2589 | @node Static Members |
e505224d PB |
2590 | @section Static Members |
2591 | ||
446e5d80 JG |
2592 | The data area for a class is a concatenation of the space used by the |
2593 | data members of the class. If the class has virtual methods, a vtable | |
e505224d | 2594 | pointer follows the class data. The field offset part of each field |
446e5d80 | 2595 | description in the class stab shows this ordering. |
e505224d | 2596 | |
446e5d80 | 2597 | << How is this reflected in stabs? See Cygnus bug #677 for some info. >> |
e505224d | 2598 | |
899bafeb | 2599 | @node Example2.c |
e505224d PB |
2600 | @appendix Example2.c - source code for extended example |
2601 | ||
2602 | @example | |
2603 | 1 char g_foo = 'c'; | |
2604 | 2 register int g_bar asm ("%g5"); | |
2605 | 3 static int s_g_repeat = 2; | |
2606 | 4 int (*g_pf)(); | |
2607 | 5 | |
2608 | 6 struct s_tag @{ | |
2609 | 7 int s_int; | |
2610 | 8 float s_float; | |
2611 | 9 char s_char_vec[8]; | |
2612 | 10 struct s_tag* s_next; | |
2613 | 11 @} g_an_s; | |
2614 | 12 | |
2615 | 13 typedef struct s_tag s_typedef; | |
2616 | 14 | |
2617 | 15 char char_vec[3] = @{'a','b','c'@}; | |
2618 | 16 | |
2619 | 17 main (argc, argv) | |
2620 | 18 int argc; | |
2621 | 19 char* argv[]; | |
2622 | 20 @{ | |
2623 | 21 static float s_flap; | |
139741da RP |
2624 | 22 int times; |
2625 | 23 for (times=0; times < s_g_repeat; times++)@{ | |
2626 | 24 int inner; | |
2627 | 25 printf ("Hello world\n"); | |
2628 | 26 @} | |
e505224d PB |
2629 | 27 @}; |
2630 | 28 | |
2631 | 29 enum e_places @{first,second=3,last@}; | |
2632 | 30 | |
2633 | 31 static s_proc (s_arg, s_ptr_arg, char_vec) | |
2634 | 32 s_typedef s_arg; | |
2635 | 33 s_typedef* s_ptr_arg; | |
2636 | 34 char* char_vec; | |
2637 | 35 @{ | |
2638 | 36 union u_tag @{ | |
2639 | 37 int u_int; | |
2640 | 38 float u_float; | |
2641 | 39 char* u_char; | |
2642 | 40 @} an_u; | |
2643 | 41 @} | |
2644 | 42 | |
2645 | 43 | |
2646 | @end example | |
2647 | ||
899bafeb | 2648 | @node Example2.s |
e505224d PB |
2649 | @appendix Example2.s - assembly code for extended example |
2650 | ||
2651 | @example | |
2652 | 1 gcc2_compiled.: | |
2653 | 2 .stabs "/cygint/s1/users/jcm/play/",100,0,0,Ltext0 | |
2654 | 3 .stabs "example2.c",100,0,0,Ltext0 | |
139741da | 2655 | 4 .text |
e505224d PB |
2656 | 5 Ltext0: |
2657 | 6 .stabs "int:t1=r1;-2147483648;2147483647;",128,0,0,0 | |
2658 | 7 .stabs "char:t2=r2;0;127;",128,0,0,0 | |
2659 | 8 .stabs "long int:t3=r1;-2147483648;2147483647;",128,0,0,0 | |
2660 | 9 .stabs "unsigned int:t4=r1;0;-1;",128,0,0,0 | |
2661 | 10 .stabs "long unsigned int:t5=r1;0;-1;",128,0,0,0 | |
2662 | 11 .stabs "short int:t6=r1;-32768;32767;",128,0,0,0 | |
2663 | 12 .stabs "long long int:t7=r1;0;-1;",128,0,0,0 | |
2664 | 13 .stabs "short unsigned int:t8=r1;0;65535;",128,0,0,0 | |
2665 | 14 .stabs "long long unsigned int:t9=r1;0;-1;",128,0,0,0 | |
2666 | 15 .stabs "signed char:t10=r1;-128;127;",128,0,0,0 | |
2667 | 16 .stabs "unsigned char:t11=r1;0;255;",128,0,0,0 | |
2668 | 17 .stabs "float:t12=r1;4;0;",128,0,0,0 | |
2669 | 18 .stabs "double:t13=r1;8;0;",128,0,0,0 | |
2670 | 19 .stabs "long double:t14=r1;8;0;",128,0,0,0 | |
2671 | 20 .stabs "void:t15=15",128,0,0,0 | |
2672 | 21 .stabs "g_foo:G2",32,0,0,0 | |
139741da RP |
2673 | 22 .global _g_foo |
2674 | 23 .data | |
e505224d | 2675 | 24 _g_foo: |
139741da | 2676 | 25 .byte 99 |
e505224d | 2677 | 26 .stabs "s_g_repeat:S1",38,0,0,_s_g_repeat |
139741da | 2678 | 27 .align 4 |
e505224d | 2679 | 28 _s_g_repeat: |
139741da | 2680 | 29 .word 2 |
5bc927fb RP |
2681 | @c FIXME! fake linebreak in line 30 |
2682 | 30 .stabs "s_tag:T16=s20s_int:1,0,32;s_float:12,32,32;s_char_vec: | |
2683 | 17=ar1;0;7;2,64,64;s_next:18=*16,128,32;;",128,0,0,0 | |
e505224d PB |
2684 | 31 .stabs "s_typedef:t16",128,0,0,0 |
2685 | 32 .stabs "char_vec:G19=ar1;0;2;2",32,0,0,0 | |
139741da RP |
2686 | 33 .global _char_vec |
2687 | 34 .align 4 | |
e505224d | 2688 | 35 _char_vec: |
139741da RP |
2689 | 36 .byte 97 |
2690 | 37 .byte 98 | |
2691 | 38 .byte 99 | |
2692 | 39 .reserve _s_flap.0,4,"bss",4 | |
2693 | 40 .text | |
2694 | 41 .align 4 | |
e505224d | 2695 | 42 LC0: |
139741da RP |
2696 | 43 .ascii "Hello world\12\0" |
2697 | 44 .align 4 | |
2698 | 45 .global _main | |
2699 | 46 .proc 1 | |
e505224d PB |
2700 | 47 _main: |
2701 | 48 .stabn 68,0,20,LM1 | |
2702 | 49 LM1: | |
139741da RP |
2703 | 50 !#PROLOGUE# 0 |
2704 | 51 save %sp,-144,%sp | |
2705 | 52 !#PROLOGUE# 1 | |
2706 | 53 st %i0,[%fp+68] | |
2707 | 54 st %i1,[%fp+72] | |
2708 | 55 call ___main,0 | |
2709 | 56 nop | |
e505224d PB |
2710 | 57 LBB2: |
2711 | 58 .stabn 68,0,23,LM2 | |
2712 | 59 LM2: | |
139741da | 2713 | 60 st %g0,[%fp-20] |
e505224d | 2714 | 61 L2: |
139741da RP |
2715 | 62 sethi %hi(_s_g_repeat),%o0 |
2716 | 63 ld [%fp-20],%o1 | |
2717 | 64 ld [%o0+%lo(_s_g_repeat)],%o0 | |
2718 | 65 cmp %o1,%o0 | |
2719 | 66 bge L3 | |
2720 | 67 nop | |
e505224d PB |
2721 | 68 LBB3: |
2722 | 69 .stabn 68,0,25,LM3 | |
2723 | 70 LM3: | |
139741da RP |
2724 | 71 sethi %hi(LC0),%o1 |
2725 | 72 or %o1,%lo(LC0),%o0 | |
2726 | 73 call _printf,0 | |
2727 | 74 nop | |
e505224d PB |
2728 | 75 .stabn 68,0,26,LM4 |
2729 | 76 LM4: | |
2730 | 77 LBE3: | |
2731 | 78 .stabn 68,0,23,LM5 | |
2732 | 79 LM5: | |
2733 | 80 L4: | |
139741da RP |
2734 | 81 ld [%fp-20],%o0 |
2735 | 82 add %o0,1,%o1 | |
2736 | 83 st %o1,[%fp-20] | |
2737 | 84 b,a L2 | |
e505224d PB |
2738 | 85 L3: |
2739 | 86 .stabn 68,0,27,LM6 | |
2740 | 87 LM6: | |
2741 | 88 LBE2: | |
2742 | 89 .stabn 68,0,27,LM7 | |
2743 | 90 LM7: | |
2744 | 91 L1: | |
139741da RP |
2745 | 92 ret |
2746 | 93 restore | |
e505224d PB |
2747 | 94 .stabs "main:F1",36,0,0,_main |
2748 | 95 .stabs "argc:p1",160,0,0,68 | |
2749 | 96 .stabs "argv:p20=*21=*2",160,0,0,72 | |
2750 | 97 .stabs "s_flap:V12",40,0,0,_s_flap.0 | |
2751 | 98 .stabs "times:1",128,0,0,-20 | |
2752 | 99 .stabn 192,0,0,LBB2 | |
2753 | 100 .stabs "inner:1",128,0,0,-24 | |
2754 | 101 .stabn 192,0,0,LBB3 | |
2755 | 102 .stabn 224,0,0,LBE3 | |
2756 | 103 .stabn 224,0,0,LBE2 | |
2757 | 104 .stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0 | |
5bc927fb RP |
2758 | @c FIXME: fake linebreak in line 105 |
2759 | 105 .stabs "u_tag:T23=u4u_int:1,0,32;u_float:12,0,32;u_char:21,0,32;;", | |
2760 | 128,0,0,0 | |
139741da RP |
2761 | 106 .align 4 |
2762 | 107 .proc 1 | |
e505224d PB |
2763 | 108 _s_proc: |
2764 | 109 .stabn 68,0,35,LM8 | |
2765 | 110 LM8: | |
139741da RP |
2766 | 111 !#PROLOGUE# 0 |
2767 | 112 save %sp,-120,%sp | |
2768 | 113 !#PROLOGUE# 1 | |
2769 | 114 mov %i0,%o0 | |
2770 | 115 st %i1,[%fp+72] | |
2771 | 116 st %i2,[%fp+76] | |
e505224d PB |
2772 | 117 LBB4: |
2773 | 118 .stabn 68,0,41,LM9 | |
2774 | 119 LM9: | |
2775 | 120 LBE4: | |
2776 | 121 .stabn 68,0,41,LM10 | |
2777 | 122 LM10: | |
2778 | 123 L5: | |
139741da RP |
2779 | 124 ret |
2780 | 125 restore | |
e505224d PB |
2781 | 126 .stabs "s_proc:f1",36,0,0,_s_proc |
2782 | 127 .stabs "s_arg:p16",160,0,0,0 | |
2783 | 128 .stabs "s_ptr_arg:p18",160,0,0,72 | |
2784 | 129 .stabs "char_vec:p21",160,0,0,76 | |
2785 | 130 .stabs "an_u:23",128,0,0,-20 | |
2786 | 131 .stabn 192,0,0,LBB4 | |
2787 | 132 .stabn 224,0,0,LBE4 | |
2788 | 133 .stabs "g_bar:r1",64,0,0,5 | |
2789 | 134 .stabs "g_pf:G24=*25=f1",32,0,0,0 | |
139741da | 2790 | 135 .common _g_pf,4,"bss" |
e505224d | 2791 | 136 .stabs "g_an_s:G16",32,0,0,0 |
139741da | 2792 | 137 .common _g_an_s,20,"bss" |
e505224d PB |
2793 | @end example |
2794 | ||
899bafeb | 2795 | @node Stab types |
8c59ee11 | 2796 | @appendix Table A: Symbol types from stabs |
e505224d PB |
2797 | |
2798 | Table A lists stab types sorted by type number. Stab type numbers are | |
2799 | 32 and greater. This is the full list of stab numbers, including stab | |
2800 | types that are used in languages other than C. | |
2801 | ||
2802 | The #define names for these stab types are defined in: | |
2803 | devo/include/aout/stab.def | |
2804 | ||
899bafeb | 2805 | @smallexample |
e505224d PB |
2806 | type type #define used to describe |
2807 | dec hex name source program feature | |
5bc927fb | 2808 | ------------------------------------------------ |
139741da RP |
2809 | 32 0x20 N_GYSM global symbol |
2810 | 34 0X22 N_FNAME function name (for BSD Fortran) | |
2811 | 36 0x24 N_FUN function name or text segment variable for C | |
2812 | 38 0x26 N_STSYM static symbol (data segment w/internal linkage) | |
2813 | 40 0x28 N_LCSYM .lcomm symbol(BSS-seg variable w/internal linkage) | |
2814 | 42 0x2a N_MAIN Name of main routine (not used in C) | |
2815 | 48 0x30 N_PC global symbol (for Pascal) | |
2816 | 50 0x32 N_NSYMS number of symbols (according to Ultrix V4.0) | |
2817 | 52 0x34 N_NOMAP no DST map for sym (according to Ultrix V4.0) | |
2818 | 64 0x40 N_RSYM register variable | |
2819 | 66 0x42 N_M2C Modula-2 compilation unit | |
2820 | 68 0x44 N_SLINE line number in text segment | |
2821 | 70 0x46 N_DSLINE line number in data segment | |
2822 | ||
2823 | 72 0x48 N_BSLINE line number in bss segment | |
2824 | 72 0x48 N_BROWS Sun source code browser, path to .cb file | |
2825 | ||
2826 | 74 0x4a N_DEFD GNU Modula2 definition module dependency | |
2827 | ||
2828 | 80 0x50 N_EHDECL GNU C++ exception variable | |
2829 | 80 0x50 N_MOD2 Modula2 info "for imc" (according to Ultrix V4.0) | |
2830 | ||
2831 | 84 0x54 N_CATCH GNU C++ "catch" clause | |
2832 | 96 0x60 N_SSYM structure of union element | |
2833 | 100 0x64 N_SO path and name of source file | |
2834 | 128 0x80 N_LSYM automatic var in the stack | |
2835 | (also used for type desc.) | |
2836 | 130 0x82 N_BINCL beginning of an include file (Sun only) | |
2837 | 132 0x84 N_SOL Name of sub-source (#include) file. | |
2838 | 160 0xa0 N_PSYM parameter variable | |
2839 | 162 0xa2 N_EINCL end of an include file | |
2840 | 164 0xa4 N_ENTRY alternate entry point | |
2841 | 192 0xc0 N_LBRAC beginning of a lexical block | |
2842 | 194 0xc2 N_EXCL place holder for a deleted include file | |
2843 | 196 0xc4 N_SCOPE modula2 scope information (Sun linker) | |
2844 | 224 0xe0 N_RBRAC end of a lexical block | |
2845 | 226 0xe2 N_BCOMM begin named common block | |
2846 | 228 0xe4 N_ECOMM end named common block | |
2847 | 232 0xe8 N_ECOML end common (local name) | |
e505224d PB |
2848 | |
2849 | << used on Gould systems for non-base registers syms >> | |
139741da RP |
2850 | 240 0xf0 N_NBTEXT ?? |
2851 | 242 0xf2 N_NBDATA ?? | |
2852 | 244 0xf4 N_NBBSS ?? | |
2853 | 246 0xf6 N_NBSTS ?? | |
2854 | 248 0xf8 N_NBLCS ?? | |
899bafeb | 2855 | @end smallexample |
e505224d | 2856 | |
899bafeb | 2857 | @node Assembler types |
8c59ee11 | 2858 | @appendix Table B: Symbol types from assembler and linker |
e505224d PB |
2859 | |
2860 | Table B shows the types of symbol table entries that hold assembler | |
2861 | and linker symbols. | |
2862 | ||
2863 | The #define names for these n_types values are defined in | |
2864 | /include/aout/aout64.h | |
2865 | ||
899bafeb | 2866 | @smallexample |
139741da RP |
2867 | dec hex #define |
2868 | n_type n_type name used to describe | |
5bc927fb | 2869 | ------------------------------------------ |
139741da RP |
2870 | 1 0x0 N_UNDF undefined symbol |
2871 | 2 0x2 N_ABS absolute symbol -- defined at a particular address | |
2872 | 3 0x3 extern " (vs. file scope) | |
2873 | 4 0x4 N_TEXT text symbol -- defined at offset in text segment | |
2874 | 5 0x5 extern " (vs. file scope) | |
2875 | 6 0x6 N_DATA data symbol -- defined at offset in data segment | |
2876 | 7 0x7 extern " (vs. file scope) | |
2877 | 8 0x8 N_BSS BSS symbol -- defined at offset in zero'd segment | |
2878 | 9 extern " (vs. file scope) | |
2879 | ||
2880 | 12 0x0C N_FN_SEQ func name for Sequent compilers (stab exception) | |
2881 | ||
2882 | 49 0x12 N_COMM common sym -- visable after shared lib dynamic link | |
2883 | 31 0x1f N_FN file name of a .o file | |
899bafeb | 2884 | @end smallexample |
e505224d | 2885 | |
8c59ee11 JK |
2886 | @node Symbol Descriptors |
2887 | @appendix Table C: Symbol descriptors | |
e505224d | 2888 | |
ed9708e2 | 2889 | @c Please keep this alphabetical |
497e44a5 | 2890 | @table @code |
8c59ee11 JK |
2891 | @item @var{(digit)} |
2892 | @itemx ( | |
2893 | @itemx - | |
497e44a5 JK |
2894 | Local variable, @xref{Automatic variables}. |
2895 | ||
6897f9ec JK |
2896 | @item a |
2897 | Parameter passed by reference in register, @xref{Parameters}. | |
2898 | ||
2899 | @item c | |
2900 | Constant, @xref{Constants}. | |
2901 | ||
ed9708e2 | 2902 | @item C |
8c59ee11 JK |
2903 | Conformant array bound (Pascal, maybe other languages), |
2904 | @xref{Parameters}. Name of a caught exception (GNU C++). These can be | |
2905 | distinguished because the latter uses N_CATCH and the former uses | |
2906 | another symbol type. | |
6897f9ec JK |
2907 | |
2908 | @item d | |
2909 | Floating point register variable, @xref{Register variables}. | |
2910 | ||
2911 | @item D | |
2912 | Parameter in floating point register, @xref{Parameters}. | |
ed9708e2 | 2913 | |
497e44a5 | 2914 | @item f |
6897f9ec | 2915 | Static function, @xref{Procedures}. |
497e44a5 JK |
2916 | |
2917 | @item F | |
2918 | Global function, @xref{Procedures}. | |
2919 | ||
497e44a5 JK |
2920 | @item G |
2921 | Global variable, @xref{Global Variables}. | |
2922 | ||
ed9708e2 JK |
2923 | @item i |
2924 | @xref{Parameters}. | |
2925 | ||
6897f9ec JK |
2926 | @item I |
2927 | Internal (nested) procedure, @xref{Procedures}. | |
2928 | ||
2929 | @item J | |
2930 | Internal (nested) function, @xref{Procedures}. | |
2931 | ||
2932 | @item L | |
2933 | Label name (documented by AIX, no further information known). | |
2934 | ||
2935 | @item m | |
2936 | Module, @xref{Procedures}. | |
2937 | ||
ed9708e2 | 2938 | @item p |
8c59ee11 | 2939 | Argument list parameter, @xref{Parameters}. |
ed9708e2 JK |
2940 | |
2941 | @item pP | |
2942 | @xref{Parameters}. | |
2943 | ||
2944 | @item pF | |
8c59ee11 | 2945 | FORTRAN Function parameter, @xref{Parameters}. |
ed9708e2 JK |
2946 | |
2947 | @item P | |
1a8b5668 JK |
2948 | Unfortunately, three separate meanings have been independently invented |
2949 | for this symbol descriptor. At least the GNU and Sun uses can be | |
2950 | distinguished by the symbol type. Global Procedure (AIX) (symbol type | |
2951 | used unknown), @xref{Procedures}. Register parameter (GNU) (symbol type | |
2952 | N_PSYM), @xref{Parameters}. Prototype of function referenced by this | |
2953 | file (Sun acc) (symbol type N_FUN). | |
6897f9ec JK |
2954 | |
2955 | @item Q | |
2956 | Static Procedure, @xref{Procedures}. | |
2957 | ||
2958 | @item R | |
ed9708e2 JK |
2959 | Register parameter @xref{Parameters}. |
2960 | ||
497e44a5 JK |
2961 | @item r |
2962 | Register variable, @xref{Register variables}. | |
2963 | ||
2964 | @item S | |
2965 | Static file scope variable @xref{Initialized statics}, | |
1b5c6c05 | 2966 | @xref{Un-initialized statics}. |
497e44a5 | 2967 | |
ed9708e2 JK |
2968 | @item t |
2969 | Type name, @xref{Typedefs}. | |
2970 | ||
2971 | @item T | |
8c59ee11 | 2972 | enumeration, struct or union tag, @xref{Typedefs}. |
ed9708e2 JK |
2973 | |
2974 | @item v | |
8c59ee11 | 2975 | Parameter passed by reference, @xref{Parameters}. |
ed9708e2 | 2976 | |
497e44a5 JK |
2977 | @item V |
2978 | Static procedure scope variable @xref{Initialized statics}, | |
1b5c6c05 | 2979 | @xref{Un-initialized statics}. |
497e44a5 | 2980 | |
6897f9ec JK |
2981 | @item x |
2982 | Conformant array, @xref{Parameters}. | |
2983 | ||
ed9708e2 JK |
2984 | @item X |
2985 | Function return variable, @xref{Parameters}. | |
497e44a5 | 2986 | @end table |
e505224d | 2987 | |
899bafeb | 2988 | @node Type Descriptors |
8c59ee11 | 2989 | @appendix Table D: Type Descriptors |
e505224d | 2990 | |
6897f9ec | 2991 | @table @code |
8c59ee11 JK |
2992 | @item @var{digit} |
2993 | @itemx ( | |
2994 | Type reference, @xref{Stabs Format}. | |
2995 | ||
2996 | @item - | |
2997 | Reference to builtin type, @xref{Negative Type Numbers}. | |
2998 | ||
2999 | @item # | |
3000 | Method (C++), @xref{Cplusplus}. | |
6897f9ec JK |
3001 | |
3002 | @item * | |
8c59ee11 JK |
3003 | Pointer, @xref{Miscellaneous Types}. |
3004 | ||
3005 | @item & | |
3006 | Reference (C++). | |
6897f9ec JK |
3007 | |
3008 | @item @@ | |
8c59ee11 JK |
3009 | Type Attributes (AIX), @xref{Stabs Format}. Member (class and variable) |
3010 | type (GNU C++), @xref{Cplusplus}. | |
e505224d | 3011 | |
6897f9ec | 3012 | @item a |
8c59ee11 JK |
3013 | Array, @xref{Arrays}. |
3014 | ||
3015 | @item A | |
3016 | Open array, @xref{Arrays}. | |
3017 | ||
3018 | @item b | |
3019 | Pascal space type (AIX), @xref{Miscellaneous Types}. Builtin integer | |
3020 | type (Sun), @xref{Builtin Type Descriptors}. | |
3021 | ||
3022 | @item B | |
3023 | Volatile-qualified type, @xref{Miscellaneous Types}. | |
3024 | ||
3025 | @item c | |
3026 | Complex builtin type, @xref{Builtin Type Descriptors}. | |
3027 | ||
3028 | @item C | |
3029 | COBOL Picture type. See AIX documentation for details. | |
3030 | ||
3031 | @item d | |
3032 | File type, @xref{Miscellaneous Types}. | |
3033 | ||
3034 | @item D | |
3035 | N-dimensional dynamic array, @xref{Arrays}. | |
6897f9ec JK |
3036 | |
3037 | @item e | |
8c59ee11 JK |
3038 | Enumeration type, @xref{Enumerations}. |
3039 | ||
3040 | @item E | |
3041 | N-dimensional subarray, @xref{Arrays}. | |
6897f9ec JK |
3042 | |
3043 | @item f | |
8c59ee11 JK |
3044 | Function type, @xref{Function types}. |
3045 | ||
3046 | @item g | |
3047 | Builtin floating point type, @xref{Builtin Type Descriptors}. | |
3048 | ||
3049 | @item G | |
3050 | COBOL Group. See AIX documentation for details. | |
3051 | ||
3052 | @item i | |
3053 | Imported type, @xref{Cross-references}. | |
3054 | ||
3055 | @item k | |
3056 | Const-qualified type, @xref{Miscellaneous Types}. | |
3057 | ||
3058 | @item K | |
3059 | COBOL File Descriptor. See AIX documentation for details. | |
3060 | ||
3061 | @item n | |
3062 | String type, @xref{Strings}. | |
3063 | ||
3064 | @item N | |
3065 | Stringptr, @xref{Strings}. | |
3066 | ||
3067 | @item M | |
3068 | Multiple instance type, @xref{Miscellaneous Types}. | |
3069 | ||
3070 | @item o | |
3071 | Opaque type, @xref{Typedefs}. | |
3072 | ||
3073 | @item P | |
3074 | Packed array, @xref{Arrays}. | |
6897f9ec JK |
3075 | |
3076 | @item r | |
8c59ee11 JK |
3077 | Range type, @xref{Subranges}. |
3078 | ||
3079 | @item R | |
3080 | Builtin floating type, @xref{Builtin Type Descriptors}. | |
6897f9ec JK |
3081 | |
3082 | @item s | |
8c59ee11 JK |
3083 | Structure type, @xref{Structures}. |
3084 | ||
3085 | @item S | |
3086 | Set type, @xref{Miscellaneous Types}. | |
6897f9ec JK |
3087 | |
3088 | @item u | |
8c59ee11 JK |
3089 | Union, @xref{Unions}. |
3090 | ||
3091 | @item v | |
3092 | Variant record. This is a Pascal and Modula-2 feature which is like a | |
3093 | union within a struct in C. See AIX documentation for details. | |
3094 | ||
3095 | @item w | |
3096 | Wide character, @xref{Builtin Type Descriptors}. | |
3097 | ||
3098 | @item x | |
3099 | Cross-reference, @xref{Cross-references}. | |
6897f9ec | 3100 | |
8c59ee11 JK |
3101 | @item z |
3102 | gstring, @xref{Strings}. | |
6897f9ec | 3103 | @end table |
e505224d | 3104 | |
899bafeb | 3105 | @node Expanded reference |
e505224d PB |
3106 | @appendix Expanded reference by stab type. |
3107 | ||
8c59ee11 JK |
3108 | @c FIXME: For most types this should be much shorter and much sweeter, |
3109 | @c see N_PSYM for an example. For stuff like N_SO where the stab type | |
3110 | @c really is the important thing, the information can stay here. | |
3111 | ||
3112 | @c FIXME: It probably should be merged with Tables A and B. | |
3113 | ||
e505224d PB |
3114 | Format of an entry: |
3115 | ||
3116 | The first line is the symbol type expressed in decimal, hexadecimal, | |
3117 | and as a #define (see devo/include/aout/stab.def). | |
3118 | ||
3119 | The second line describes the language constructs the symbol type | |
3120 | represents. | |
3121 | ||
3122 | The third line is the stab format with the significant stab fields | |
3123 | named and the rest NIL. | |
3124 | ||
3125 | Subsequent lines expand upon the meaning and possible values for each | |
3126 | significant stab field. # stands in for the type descriptor. | |
3127 | ||
3128 | Finally, any further information. | |
3129 | ||
899bafeb RP |
3130 | @menu |
3131 | * N_GSYM:: Global variable | |
3132 | * N_FNAME:: Function name (BSD Fortran) | |
3133 | * N_FUN:: C Function name or text segment variable | |
3134 | * N_STSYM:: Initialized static symbol | |
3135 | * N_LCSYM:: Uninitialized static symbol | |
3136 | * N_MAIN:: Name of main routine (not for C) | |
3137 | * N_PC:: Pascal global symbol | |
3138 | * N_NSYMS:: Number of symbols | |
3139 | * N_NOMAP:: No DST map | |
3140 | * N_RSYM:: Register variable | |
3141 | * N_M2C:: Modula-2 compilation unit | |
3142 | * N_SLINE:: Line number in text segment | |
3143 | * N_DSLINE:: Line number in data segment | |
3144 | * N_BSLINE:: Line number in bss segment | |
3145 | * N_BROWS:: Path to .cb file for Sun source code browser | |
3146 | * N_DEFD:: GNU Modula2 definition module dependency | |
3147 | * N_EHDECL:: GNU C++ exception variable | |
3148 | * N_MOD2:: Modula2 information "for imc" | |
3149 | * N_CATCH:: GNU C++ "catch" clause | |
3150 | * N_SSYM:: Structure or union element | |
3151 | * N_SO:: Source file containing main | |
3152 | * N_LSYM:: Automatic variable | |
3153 | * N_BINCL:: Beginning of include file (Sun only) | |
3154 | * N_SOL:: Name of include file | |
3155 | * N_PSYM:: Parameter variable | |
3156 | * N_EINCL:: End of include file | |
3157 | * N_ENTRY:: Alternate entry point | |
3158 | * N_LBRAC:: Beginning of lexical block | |
3159 | * N_EXCL:: Deleted include file | |
3160 | * N_SCOPE:: Modula2 scope information (Sun only) | |
3161 | * N_RBRAC:: End of lexical block | |
3162 | * N_BCOMM:: Begin named common block | |
3163 | * N_ECOMM:: End named common block | |
3164 | * N_ECOML:: End common | |
3165 | * Gould:: non-base register symbols used on Gould systems | |
3166 | * N_LENG:: Length of preceding entry | |
3167 | @end menu | |
3168 | ||
3169 | @node N_GSYM | |
139741da | 3170 | @section 32 - 0x20 - N_GYSM |
899bafeb RP |
3171 | |
3172 | @display | |
e505224d PB |
3173 | Global variable. |
3174 | ||
3175 | .stabs "name", N_GSYM, NIL, NIL, NIL | |
899bafeb | 3176 | @end display |
e505224d | 3177 | |
899bafeb | 3178 | @example |
e505224d | 3179 | "name" -> "symbol_name:#type" |
139741da | 3180 | # -> G |
899bafeb | 3181 | @end example |
e505224d | 3182 | |
4d7f562d | 3183 | Only the "name" field is significant. The location of the variable is |
e505224d PB |
3184 | obtained from the corresponding external symbol. |
3185 | ||
899bafeb RP |
3186 | @node N_FNAME |
3187 | @section 34 - 0x22 - N_FNAME | |
e505224d PB |
3188 | Function name (for BSD Fortran) |
3189 | ||
899bafeb | 3190 | @display |
e505224d | 3191 | .stabs "name", N_FNAME, NIL, NIL, NIL |
899bafeb | 3192 | @end display |
e505224d | 3193 | |
899bafeb | 3194 | @example |
e505224d | 3195 | "name" -> "function_name" |
899bafeb | 3196 | @end example |
e505224d PB |
3197 | |
3198 | Only the "name" field is significant. The location of the symbol is | |
3199 | obtained from the corresponding extern symbol. | |
3200 | ||
899bafeb | 3201 | @node N_FUN |
6897f9ec | 3202 | @section 36 - 0x24 - N_FUN |
e505224d | 3203 | |
6897f9ec JK |
3204 | Function name (@pxref{Procedures}) or text segment variable |
3205 | (@pxref{Variables}). | |
899bafeb RP |
3206 | @example |
3207 | @exdent @emph{For functions:} | |
e505224d | 3208 | "name" -> "proc_name:#return_type" |
139741da RP |
3209 | # -> F (global function) |
3210 | f (local function) | |
e505224d PB |
3211 | desc -> line num for proc start. (GCC doesn't set and DBX doesn't miss it.) |
3212 | value -> Code address of proc start. | |
3213 | ||
899bafeb | 3214 | @exdent @emph{For text segment variables:} |
e505224d | 3215 | <<How to create one?>> |
899bafeb | 3216 | @end example |
e505224d | 3217 | |
899bafeb RP |
3218 | @node N_STSYM |
3219 | @section 38 - 0x26 - N_STSYM | |
e505224d PB |
3220 | Initialized static symbol (data segment w/internal linkage). |
3221 | ||
899bafeb | 3222 | @display |
e505224d | 3223 | .stabs "name", N_STSYM, NIL, NIL, value |
899bafeb | 3224 | @end display |
e505224d | 3225 | |
899bafeb | 3226 | @example |
e505224d | 3227 | "name" -> "symbol_name#type" |
139741da RP |
3228 | # -> S (scope global to compilation unit) |
3229 | -> V (scope local to a procedure) | |
e505224d | 3230 | value -> Data Address |
899bafeb | 3231 | @end example |
e505224d | 3232 | |
899bafeb RP |
3233 | @node N_LCSYM |
3234 | @section 40 - 0x28 - N_LCSYM | |
e505224d PB |
3235 | Unitialized static (.lcomm) symbol(BSS segment w/internal linkage). |
3236 | ||
899bafeb | 3237 | @display |
e505224d | 3238 | .stabs "name", N_LCLSYM, NIL, NIL, value |
899bafeb | 3239 | @end display |
e505224d | 3240 | |
899bafeb | 3241 | @example |
e505224d | 3242 | "name" -> "symbol_name#type" |
139741da RP |
3243 | # -> S (scope global to compilation unit) |
3244 | -> V (scope local to procedure) | |
e505224d | 3245 | value -> BSS Address |
899bafeb | 3246 | @end example |
e505224d | 3247 | |
899bafeb | 3248 | @node N_MAIN |
139741da | 3249 | @section 42 - 0x2a - N_MAIN |
e505224d PB |
3250 | Name of main routine (not used in C) |
3251 | ||
899bafeb | 3252 | @display |
e505224d | 3253 | .stabs "name", N_MAIN, NIL, NIL, NIL |
899bafeb | 3254 | @end display |
e505224d | 3255 | |
899bafeb | 3256 | @example |
e505224d | 3257 | "name" -> "name_of_main_routine" |
899bafeb | 3258 | @end example |
e505224d | 3259 | |
899bafeb | 3260 | @node N_PC |
139741da | 3261 | @section 48 - 0x30 - N_PC |
e505224d PB |
3262 | Global symbol (for Pascal) |
3263 | ||
899bafeb | 3264 | @display |
e505224d | 3265 | .stabs "name", N_PC, NIL, NIL, value |
899bafeb | 3266 | @end display |
e505224d | 3267 | |
899bafeb | 3268 | @example |
e505224d PB |
3269 | "name" -> "symbol_name" <<?>> |
3270 | value -> supposedly the line number (stab.def is skeptical) | |
899bafeb | 3271 | @end example |
e505224d | 3272 | |
899bafeb | 3273 | @display |
e505224d PB |
3274 | stabdump.c says: |
3275 | ||
3276 | global pascal symbol: name,,0,subtype,line | |
3277 | << subtype? >> | |
899bafeb | 3278 | @end display |
e505224d | 3279 | |
899bafeb | 3280 | @node N_NSYMS |
139741da | 3281 | @section 50 - 0x32 - N_NSYMS |
e505224d PB |
3282 | Number of symbols (according to Ultrix V4.0) |
3283 | ||
899bafeb | 3284 | @display |
139741da | 3285 | 0, files,,funcs,lines (stab.def) |
899bafeb | 3286 | @end display |
e505224d | 3287 | |
899bafeb RP |
3288 | @node N_NOMAP |
3289 | @section 52 - 0x34 - N_NOMAP | |
e505224d PB |
3290 | no DST map for sym (according to Ultrix V4.0) |
3291 | ||
899bafeb | 3292 | @display |
139741da | 3293 | name, ,0,type,ignored (stab.def) |
899bafeb RP |
3294 | @end display |
3295 | ||
3296 | @node N_RSYM | |
139741da | 3297 | @section 64 - 0x40 - N_RSYM |
e505224d PB |
3298 | register variable |
3299 | ||
899bafeb | 3300 | @display |
e505224d | 3301 | .stabs "name:type",N_RSYM,0,RegSize,RegNumber (Sun doc) |
899bafeb | 3302 | @end display |
e505224d | 3303 | |
899bafeb | 3304 | @node N_M2C |
139741da | 3305 | @section 66 - 0x42 - N_M2C |
e505224d PB |
3306 | Modula-2 compilation unit |
3307 | ||
899bafeb | 3308 | @display |
e505224d | 3309 | .stabs "name", N_M2C, 0, desc, value |
899bafeb | 3310 | @end display |
e505224d | 3311 | |
899bafeb | 3312 | @example |
e505224d PB |
3313 | "name" -> "unit_name,unit_time_stamp[,code_time_stamp] |
3314 | desc -> unit_number | |
3315 | value -> 0 (main unit) | |
139741da | 3316 | 1 (any other unit) |
899bafeb | 3317 | @end example |
e505224d | 3318 | |
899bafeb | 3319 | @node N_SLINE |
139741da | 3320 | @section 68 - 0x44 - N_SLINE |
e505224d PB |
3321 | Line number in text segment |
3322 | ||
899bafeb | 3323 | @display |
e505224d | 3324 | .stabn N_SLINE, 0, desc, value |
899bafeb | 3325 | @end display |
e505224d | 3326 | |
899bafeb | 3327 | @example |
e505224d PB |
3328 | desc -> line_number |
3329 | value -> code_address (relocatable addr where the corresponding code starts) | |
899bafeb | 3330 | @end example |
e505224d PB |
3331 | |
3332 | For single source lines that generate discontiguous code, such as flow | |
3333 | of control statements, there may be more than one N_SLINE stab for the | |
3334 | same source line. In this case there is a stab at the start of each | |
3335 | code range, each with the same line number. | |
3336 | ||
899bafeb RP |
3337 | @node N_DSLINE |
3338 | @section 70 - 0x46 - N_DSLINE | |
e505224d PB |
3339 | Line number in data segment |
3340 | ||
899bafeb | 3341 | @display |
e505224d | 3342 | .stabn N_DSLINE, 0, desc, value |
899bafeb | 3343 | @end display |
e505224d | 3344 | |
899bafeb | 3345 | @example |
e505224d | 3346 | desc -> line_number |
899bafeb RP |
3347 | value -> data_address (relocatable addr where the corresponding code |
3348 | starts) | |
3349 | @end example | |
e505224d PB |
3350 | |
3351 | See comment for N_SLINE above. | |
3352 | ||
899bafeb RP |
3353 | @node N_BSLINE |
3354 | @section 72 - 0x48 - N_BSLINE | |
e505224d PB |
3355 | Line number in bss segment |
3356 | ||
899bafeb | 3357 | @display |
e505224d | 3358 | .stabn N_BSLINE, 0, desc, value |
899bafeb | 3359 | @end display |
e505224d | 3360 | |
899bafeb | 3361 | @example |
e505224d | 3362 | desc -> line_number |
899bafeb RP |
3363 | value -> bss_address (relocatable addr where the corresponding code |
3364 | starts) | |
3365 | @end example | |
e505224d PB |
3366 | |
3367 | See comment for N_SLINE above. | |
3368 | ||
899bafeb | 3369 | @node N_BROWS |
139741da | 3370 | @section 72 - 0x48 - N_BROWS |
e505224d PB |
3371 | Sun source code browser, path to .cb file |
3372 | ||
3373 | <<?>> | |
3374 | "path to associated .cb file" | |
3375 | ||
3376 | Note: type field value overlaps with N_BSLINE | |
3377 | ||
899bafeb | 3378 | @node N_DEFD |
139741da | 3379 | @section 74 - 0x4a - N_DEFD |
612dbd4c | 3380 | GNU Modula2 definition module dependency |
e505224d PB |
3381 | |
3382 | GNU Modula-2 definition module dependency. Value is the modification | |
3383 | time of the definition file. Other is non-zero if it is imported with | |
3384 | the GNU M2 keyword %INITIALIZE. Perhaps N_M2C can be used if there | |
3385 | are enough empty fields? | |
3386 | ||
899bafeb RP |
3387 | @node N_EHDECL |
3388 | @section 80 - 0x50 - N_EHDECL | |
612dbd4c | 3389 | GNU C++ exception variable <<?>> |
e505224d PB |
3390 | |
3391 | "name is variable name" | |
3392 | ||
3393 | Note: conflicts with N_MOD2. | |
3394 | ||
899bafeb RP |
3395 | @node N_MOD2 |
3396 | @section 80 - 0x50 - N_MOD2 | |
3397 | Modula2 info "for imc" (according to Ultrix V4.0) | |
e505224d PB |
3398 | |
3399 | Note: conflicts with N_EHDECL <<?>> | |
3400 | ||
899bafeb RP |
3401 | @node N_CATCH |
3402 | @section 84 - 0x54 - N_CATCH | |
3403 | GNU C++ "catch" clause | |
e505224d PB |
3404 | |
3405 | GNU C++ `catch' clause. Value is its address. Desc is nonzero if | |
3406 | this entry is immediately followed by a CAUGHT stab saying what | |
3407 | exception was caught. Multiple CAUGHT stabs means that multiple | |
3408 | exceptions can be caught here. If Desc is 0, it means all exceptions | |
3409 | are caught here. | |
3410 | ||
899bafeb | 3411 | @node N_SSYM |
139741da | 3412 | @section 96 - 0x60 - N_SSYM |
e505224d PB |
3413 | Structure or union element |
3414 | ||
899bafeb RP |
3415 | Value is offset in the structure. |
3416 | ||
3417 | <<?looking at structs and unions in C I didn't see these>> | |
e505224d | 3418 | |
899bafeb | 3419 | @node N_SO |
139741da | 3420 | @section 100 - 0x64 - N_SO |
e505224d PB |
3421 | Path and name of source file containing main routine |
3422 | ||
899bafeb | 3423 | @display |
e505224d | 3424 | .stabs "name", N_SO, NIL, NIL, value |
899bafeb | 3425 | @end display |
e505224d | 3426 | |
899bafeb | 3427 | @example |
c0264596 JK |
3428 | "name" -> /source/directory/ |
3429 | -> source_file | |
e505224d PB |
3430 | |
3431 | value -> the starting text address of the compilation. | |
899bafeb | 3432 | @end example |
e505224d | 3433 | |
c0264596 JK |
3434 | These are found two in a row. The name field of the first N_SO contains |
3435 | the directory that the source file is relative to. The name field of | |
3436 | the second N_SO contains the name of the source file itself. | |
3437 | ||
3438 | Only some compilers (e.g. gcc2, Sun cc) include the directory; this | |
3439 | symbol can be distinguished by the fact that it ends in a slash. | |
3440 | According to a comment in GDB's partial-stab.h, other compilers | |
3441 | (especially unnamed C++ compilers) put out useless N_SO's for | |
3442 | nonexistent source files (after the N_SO for the real source file). | |
e505224d | 3443 | |
899bafeb | 3444 | @node N_LSYM |
139741da | 3445 | @section 128 - 0x80 - N_LSYM |
e505224d PB |
3446 | Automatic var in the stack (also used for type descriptors.) |
3447 | ||
899bafeb | 3448 | @display |
e505224d | 3449 | .stabs "name" N_LSYM, NIL, NIL, value |
899bafeb | 3450 | @end display |
e505224d | 3451 | |
899bafeb RP |
3452 | @example |
3453 | @exdent @emph{For stack based local variables:} | |
e505224d PB |
3454 | |
3455 | "name" -> name of the variable | |
3456 | value -> offset from frame pointer (negative) | |
3457 | ||
899bafeb | 3458 | @exdent @emph{For type descriptors:} |
e505224d PB |
3459 | |
3460 | "name" -> "name_of_the_type:#type" | |
139741da | 3461 | # -> t |
e505224d | 3462 | |
139741da | 3463 | type -> type_ref (or) type_def |
e505224d PB |
3464 | |
3465 | type_ref -> type_number | |
3466 | type_def -> type_number=type_desc etc. | |
899bafeb | 3467 | @end example |
e505224d PB |
3468 | |
3469 | Type may be either a type reference or a type definition. A type | |
3470 | reference is a number that refers to a previously defined type. A | |
3471 | type definition is the number that will refer to this type, followed | |
3472 | by an equals sign, a type descriptor and the additional data that | |
3473 | defines the type. See the Table D for type descriptors and the | |
3474 | section on types for what data follows each type descriptor. | |
3475 | ||
899bafeb | 3476 | @node N_BINCL |
139741da | 3477 | @section 130 - 0x82 - N_BINCL |
e505224d PB |
3478 | |
3479 | Beginning of an include file (Sun only) | |
3480 | ||
3481 | Beginning of an include file. Only Sun uses this. In an object file, | |
3482 | only the name is significant. The Sun linker puts data into some of | |
3483 | the other fields. | |
3484 | ||
899bafeb RP |
3485 | @node N_SOL |
3486 | @section 132 - 0x84 - N_SOL | |
e505224d PB |
3487 | |
3488 | Name of a sub-source file (#include file). Value is starting address | |
3489 | of the compilation. | |
3490 | <<?>> | |
3491 | ||
899bafeb | 3492 | @node N_PSYM |
139741da | 3493 | @section 160 - 0xa0 - N_PSYM |
e505224d | 3494 | |
a2a2eac8 | 3495 | Parameter variable. @xref{Parameters}. |
e505224d | 3496 | |
899bafeb RP |
3497 | @node N_EINCL |
3498 | @section 162 - 0xa2 - N_EINCL | |
e505224d PB |
3499 | |
3500 | End of an include file. This and N_BINCL act as brackets around the | |
3501 | file's output. In an ojbect file, there is no significant data in | |
899bafeb | 3502 | this entry. The Sun linker puts data into some of the fields. |
e505224d PB |
3503 | <<?>> |
3504 | ||
899bafeb RP |
3505 | @node N_ENTRY |
3506 | @section 164 - 0xa4 - N_ENTRY | |
e505224d PB |
3507 | |
3508 | Alternate entry point. | |
3509 | Value is its address. | |
3510 | <<?>> | |
3511 | ||
899bafeb RP |
3512 | @node N_LBRAC |
3513 | @section 192 - 0xc0 - N_LBRAC | |
e505224d PB |
3514 | |
3515 | Beginning of a lexical block (left brace). The variable defined | |
3516 | inside the block precede the N_LBRAC symbol. Or can they follow as | |
3517 | well as long as a new N_FUNC was not encountered. <<?>> | |
3518 | ||
899bafeb | 3519 | @display |
e505224d | 3520 | .stabn N_LBRAC, NIL, NIL, value |
899bafeb | 3521 | @end display |
e505224d | 3522 | |
899bafeb | 3523 | @example |
e505224d | 3524 | value -> code address of block start. |
899bafeb | 3525 | @end example |
e505224d | 3526 | |
899bafeb RP |
3527 | @node N_EXCL |
3528 | @section 194 - 0xc2 - N_EXCL | |
e505224d PB |
3529 | |
3530 | Place holder for a deleted include file. Replaces a N_BINCL and | |
3531 | everything up to the corresponding N_EINCL. The Sun linker generates | |
3532 | these when it finds multiple indentical copies of the symbols from an | |
3533 | included file. This appears only in output from the Sun linker. | |
3534 | <<?>> | |
3535 | ||
899bafeb RP |
3536 | @node N_SCOPE |
3537 | @section 196 - 0xc4 - N_SCOPE | |
e505224d PB |
3538 | |
3539 | Modula2 scope information (Sun linker) | |
3540 | <<?>> | |
3541 | ||
899bafeb | 3542 | @node N_RBRAC |
139741da | 3543 | @section 224 - 0xe0 - N_RBRAC |
e505224d PB |
3544 | |
3545 | End of a lexical block (right brace) | |
3546 | ||
899bafeb | 3547 | @display |
e505224d | 3548 | .stabn N_RBRAC, NIL, NIL, value |
899bafeb | 3549 | @end display |
e505224d | 3550 | |
899bafeb | 3551 | @example |
e505224d | 3552 | value -> code address of the end of the block. |
899bafeb | 3553 | @end example |
e505224d | 3554 | |
899bafeb | 3555 | @node N_BCOMM |
139741da | 3556 | @section 226 - 0xe2 - N_BCOMM |
e505224d PB |
3557 | |
3558 | Begin named common block. | |
3559 | ||
3560 | Only the name is significant. | |
3561 | <<?>> | |
3562 | ||
899bafeb | 3563 | @node N_ECOMM |
139741da | 3564 | @section 228 - 0xe4 - N_ECOMM |
e505224d PB |
3565 | |
3566 | End named common block. | |
3567 | ||
3568 | Only the name is significant and it should match the N_BCOMM | |
3569 | <<?>> | |
3570 | ||
899bafeb RP |
3571 | @node N_ECOML |
3572 | @section 232 - 0xe8 - N_ECOML | |
e505224d PB |
3573 | |
3574 | End common (local name) | |
3575 | ||
3576 | value is address. | |
3577 | <<?>> | |
3578 | ||
899bafeb RP |
3579 | @node Gould |
3580 | @section Non-base registers on Gould systems | |
e505224d PB |
3581 | << used on Gould systems for non-base registers syms, values assigned |
3582 | at random, need real info from Gould. >> | |
3583 | <<?>> | |
3584 | ||
899bafeb | 3585 | @example |
139741da RP |
3586 | 240 0xf0 N_NBTEXT ?? |
3587 | 242 0xf2 N_NBDATA ?? | |
3588 | 244 0xf4 N_NBBSS ?? | |
3589 | 246 0xf6 N_NBSTS ?? | |
3590 | 248 0xf8 N_NBLCS ?? | |
899bafeb | 3591 | @end example |
e505224d | 3592 | |
899bafeb RP |
3593 | @node N_LENG |
3594 | @section - 0xfe - N_LENG | |
e505224d PB |
3595 | |
3596 | Second symbol entry containing a length-value for the preceding entry. | |
3597 | The value is the length. | |
3598 | ||
899bafeb RP |
3599 | @node Questions |
3600 | @appendix Questions and anomalies | |
e505224d PB |
3601 | |
3602 | @itemize @bullet | |
3603 | @item | |
3604 | For GNU C stabs defining local and global variables (N_LSYM and | |
3605 | N_GSYM), the desc field is supposed to contain the source line number | |
3606 | on which the variable is defined. In reality the desc field is always | |
3607 | 0. (This behavour is defined in dbxout.c and putting a line number in | |
3608 | desc is controlled by #ifdef WINNING_GDB which defaults to false). Gdb | |
3609 | supposedly uses this information if you say 'list var'. In reality | |
3610 | var can be a variable defined in the program and gdb says `function | |
3611 | var not defined' | |
3612 | ||
3613 | @item | |
612dbd4c | 3614 | In GNU C stabs there seems to be no way to differentiate tag types: |
e505224d PB |
3615 | structures, unions, and enums (symbol descriptor T) and typedefs |
3616 | (symbol descriptor t) defined at file scope from types defined locally | |
3617 | to a procedure or other more local scope. They all use the N_LSYM | |
3618 | stab type. Types defined at procedure scope are emited after the | |
139741da | 3619 | N_RBRAC of the preceding function and before the code of the |
e505224d PB |
3620 | procedure in which they are defined. This is exactly the same as |
3621 | types defined in the source file between the two procedure bodies. | |
4d7f562d | 3622 | GDB overcompensates by placing all types in block #1, the block for |
e505224d | 3623 | symbols of file scope. This is true for default, -ansi and |
4d7f562d | 3624 | -traditional compiler options. (Bugs gcc/1063, gdb/1066.) |
e505224d PB |
3625 | |
3626 | @item | |
3627 | What ends the procedure scope? Is it the proc block's N_RBRAC or the | |
3628 | next N_FUN? (I believe its the first.) | |
3629 | ||
3630 | @item | |
3631 | The comment in xcoff.h says DBX_STATIC_CONST_VAR_CODE is used for | |
3632 | static const variables. DBX_STATIC_CONST_VAR_CODE is set to N_FUN by | |
3633 | default, in dbxout.c. If included, xcoff.h redefines it to N_STSYM. | |
3634 | But testing the default behaviour, my Sun4 native example shows | |
3635 | N_STSYM not N_FUN is used to describe file static initialized | |
3636 | variables. (the code tests for TREE_READONLY(decl) && | |
3637 | !TREE_THIS_VOLATILE(decl) and if true uses DBX_STATIC_CONST_VAR_CODE). | |
3638 | ||
3639 | @item | |
3640 | Global variable stabs don't have location information. This comes | |
3641 | from the external symbol for the same variable. The external symbol | |
3642 | has a leading underbar on the _name of the variable and the stab does | |
3643 | not. How do we know these two symbol table entries are talking about | |
3644 | the same symbol when their names are different? | |
3645 | ||
3646 | @item | |
3647 | Can gcc be configured to output stabs the way the Sun compiler | |
3648 | does, so that their native debugging tools work? <NO?> It doesn't by | |
3649 | default. GDB reads either format of stab. (gcc or SunC). How about | |
3650 | dbx? | |
3651 | @end itemize | |
3652 | ||
899bafeb | 3653 | @node xcoff-differences |
e505224d PB |
3654 | @appendix Differences between GNU stabs in a.out and GNU stabs in xcoff |
3655 | ||
497e44a5 JK |
3656 | @c FIXME: Merge *all* these into the main body of the document. |
3657 | (The AIX/RS6000 native object file format is xcoff with stabs). This | |
3658 | appendix only covers those differences which are not covered in the main | |
3659 | body of this document. | |
e505224d PB |
3660 | |
3661 | @itemize @bullet | |
3662 | @item | |
3663 | Instead of .stabs, xcoff uses .stabx. | |
3664 | ||
3665 | @item | |
3666 | The data fields of an xcoff .stabx are in a different order than an | |
1a8b5668 JK |
3667 | a.out .stabs. The order is: string, value, type, sdb-type. The desc |
3668 | and null fields present in a.out stabs are missing in xcoff stabs. For | |
3669 | N_GSYM the value field is the name of the symbol. sdb-type is unused | |
3670 | with stabs; it can always be set to 0. | |
e505224d PB |
3671 | |
3672 | @item | |
5bc927fb | 3673 | BSD a.out stab types correspond to AIX xcoff storage classes. In general the |
e505224d PB |
3674 | mapping is N_STABTYPE becomes C_STABTYPE. Some stab types in a.out |
3675 | are not supported in xcoff. See Table E. for full mappings. | |
3676 | ||
3677 | exception: | |
3678 | initialised static N_STSYM and un-initialized static N_LCSYM both map | |
3679 | to the C_STSYM storage class. But the destinction is preserved | |
3680 | because in xcoff N_STSYM and N_LCSYM must be emited in a named static | |
3681 | block. Begin the block with .bs s[RW] data_section_name for N_STSYM | |
3682 | or .bs s bss_section_name for N_LCSYM. End the block with .es | |
3683 | ||
e505224d PB |
3684 | @item |
3685 | xcoff uses a .file stab type to represent the source file name. There | |
3686 | is no stab for the path to the source file. | |
3687 | ||
3688 | @item | |
3689 | xcoff uses a .line stab type to represent source lines. The format | |
3690 | is: .line line_number. | |
3691 | ||
3692 | @item | |
3693 | xcoff emits line numbers relative to the start of the current | |
3694 | function. The start of a function is marked by .bf. If a function | |
3695 | includes lines from a seperate file, then those line numbers are | |
3696 | absolute line numbers in the <<sub-?>> file being compiled. | |
3697 | ||
3698 | @item | |
3699 | The start of current include file is marked with: .bi "filename" and | |
3700 | the end marked with .ei "filename" | |
3701 | ||
3702 | @item | |
3703 | If the xcoff stab is a N_FUN (C_FUN) then follow the string field with | |
3704 | ,. instead of just , | |
e505224d PB |
3705 | @end itemize |
3706 | ||
3707 | ||
3708 | (I think that's it for .s file differences. They could stand to be | |
3709 | better presented. This is just a list of what I have noticed so far. | |
3710 | There are a *lot* of differences in the information in the symbol | |
3711 | tables of the executable and object files.) | |
3712 | ||
3713 | Table E: mapping a.out stab types to xcoff storage classes | |
3714 | ||
3715 | @example | |
139741da | 3716 | stab type storage class |
e505224d | 3717 | ------------------------------- |
139741da RP |
3718 | N_GSYM C_GSYM |
3719 | N_FNAME unknown | |
3720 | N_FUN C_FUN | |
3721 | N_STSYM C_STSYM | |
3722 | N_LCSYM C_STSYM | |
3723 | N_MAIN unkown | |
3724 | N_PC unknown | |
3725 | N_RSYM C_RSYM | |
3726 | N_RPSYM (0x8e) C_RPSYM | |
3727 | N_M2C unknown | |
3728 | N_SLINE unknown | |
3729 | N_DSLINE unknown | |
3730 | N_BSLINE unknown | |
3731 | N_BROWSE unchanged | |
3732 | N_CATCH unknown | |
3733 | N_SSYM unknown | |
3734 | N_SO unknown | |
3735 | N_LSYM C_LSYM | |
3736 | N_DECL (0x8c) C_DECL | |
3737 | N_BINCL unknown | |
3738 | N_SOL unknown | |
3739 | N_PSYM C_PSYM | |
3740 | N_EINCL unknown | |
3741 | N_ENTRY C_ENTRY | |
3742 | N_LBRAC unknown | |
3743 | N_EXCL unknown | |
3744 | N_SCOPE unknown | |
3745 | N_RBRAC unknown | |
3746 | N_BCOMM C_BCOMM | |
3747 | N_ECOMM C_ECOMM | |
3748 | N_ECOML C_ECOML | |
3749 | ||
3750 | N_LENG unknown | |
e505224d PB |
3751 | @end example |
3752 | ||
899bafeb | 3753 | @node Sun-differences |
e505224d PB |
3754 | @appendix Differences between GNU stabs and Sun native stabs. |
3755 | ||
497e44a5 JK |
3756 | @c FIXME: Merge all this stuff into the main body of the document. |
3757 | ||
e505224d PB |
3758 | @itemize @bullet |
3759 | @item | |
612dbd4c | 3760 | GNU C stabs define *all* types, file or procedure scope, as |
e505224d PB |
3761 | N_LSYM. Sun doc talks about using N_GSYM too. |
3762 | ||
e505224d PB |
3763 | @item |
3764 | Stabs describing block scopes, N_LBRAC and N_RBRAC are supposed to | |
3765 | contain the nesting level of the block in the desc field, re Sun doc. | |
497e44a5 | 3766 | GNU stabs always have 0 in that field. dbx seems not to care. |
e505224d PB |
3767 | |
3768 | @item | |
3769 | Sun C stabs use type number pairs in the format (a,b) where a is a | |
3770 | number starting with 1 and incremented for each sub-source file in the | |
3771 | compilation. b is a number starting with 1 and incremented for each | |
612dbd4c | 3772 | new type defined in the compilation. GNU C stabs use the type number |
e505224d PB |
3773 | alone, with no source file number. |
3774 | @end itemize | |
3775 | ||
3776 | @contents | |
3777 | @bye |